Checking disk space

diskspace.ps1

function CleanVariables { Get-Variable | Where-Object { $startupVariables -notcontains $_.Name } | ForEach-Object {
    try { Remove-Variable -Name "$($_.Name)" -Force -Scope "global" -ErrorAction SilentlyContinue -WarningAction SilentlyContinue }
    catch { }
    }
}

CleanVariables

<# This form was created using POSHGUI.com  a free online gui designer for PowerShell
.NAME
    Disk Space Analyzer
#>

Add-Type -AssemblyName System.Windows.Forms
[System.Windows.Forms.Application]::EnableVisualStyles()

$Form                            = New-Object system.Windows.Forms.Form
$Form.ClientSize                 = '800,800'
$Form.text                       = "Form"
$Form.TopMost                    = $false

$TB_ComputerName                 = New-Object system.Windows.Forms.TextBox
$TB_ComputerName.multiline       = $false
$TB_ComputerName.width           = 219
$TB_ComputerName.height          = 20
$TB_ComputerName.location        = New-Object System.Drawing.Point(147,145)
$TB_ComputerName.Font            = 'Microsoft Sans Serif,10'

$LB_ComputerName                 = New-Object system.Windows.Forms.Label
$LB_ComputerName.text            = "Computer Name:"
$LB_ComputerName.AutoSize        = $true
$LB_ComputerName.width           = 25
$LB_ComputerName.height          = 10
$LB_ComputerName.location        = New-Object System.Drawing.Point(34,148)
$LB_ComputerName.Font            = 'Microsoft Sans Serif,10'

$TB_UserName                     = New-Object system.Windows.Forms.TextBox
$TB_UserName.multiline           = $false
$TB_UserName.width               = 219
$TB_UserName.height              = 20
$TB_UserName.location            = New-Object System.Drawing.Point(147,172)
$TB_UserName.Font                = 'Microsoft Sans Serif,10'

$LB_UserName                     = New-Object system.Windows.Forms.Label
$LB_UserName.text                = "User Name:"
$LB_UserName.AutoSize            = $true
$LB_UserName.width               = 25
$LB_UserName.height              = 10
$LB_UserName.location            = New-Object System.Drawing.Point(34,175)
$LB_UserName.Font                = 'Microsoft Sans Serif,10'

$LB_INFO                         = New-Object system.Windows.Forms.Label
$LB_INFO.text                    = "Please enter the Computer Name and User Name below and press `"RUN!`""
$LB_INFO.AutoSize                = $true
$LB_INFO.width                   = 25
$LB_INFO.height                  = 10
$LB_INFO.location                = New-Object System.Drawing.Point(34,81)
$LB_INFO.Font                    = 'Microsoft Sans Serif,10'

$LB_TITLE                        = New-Object system.Windows.Forms.Label
$LB_TITLE.text                   = "DISK SPACE ANALYZER v0.1b"
$LB_TITLE.AutoSize               = $true
$LB_TITLE.width                  = 25
$LB_TITLE.height                 = 10
$LB_TITLE.location               = New-Object System.Drawing.Point(137,20)
$LB_TITLE.Font                   = 'Microsoft Sans Serif,20'

$BTN_RUN                         = New-Object system.Windows.Forms.Button
$BTN_RUN.text                    = "RUN!"
$BTN_RUN.width                   = 60
$BTN_RUN.height                  = 30
$BTN_RUN.location                = New-Object System.Drawing.Point(147,209)
$BTN_RUN.Font                    = 'Microsoft Sans Serif,10'

$BTN_SAVE                         = New-Object system.Windows.Forms.Button
$BTN_SAVE.text                    = "SAVE"
$BTN_SAVE.width                   = 60
$BTN_SAVE.height                  = 30
$BTN_SAVE.location                = New-Object System.Drawing.Point(207,209)
$BTN_SAVE.Font                    = 'Microsoft Sans Serif,10'

$BTN_Cancel                      = New-Object system.Windows.Forms.Button
$BTN_Cancel.text                 = "CLOSE"
$BTN_Cancel.width                = 60
$BTN_Cancel.height               = 30
$BTN_Cancel.location             = New-Object System.Drawing.Point(267,209)
$BTN_Cancel.Font                 = 'Microsoft Sans Serif,10'

$LB_Status                       = New-Object system.Windows.Forms.Label
$LB_Status.text                  = "Status: "
$LB_Status.AutoSize              = $true
$LB_Status.width                 = 25
$LB_Status.height                = 10
$LB_Status.location              = New-Object System.Drawing.Point(34,113)
$LB_Status.Font                  = 'Microsoft Sans Serif,10,style=Bold'

$LB_StatusUpdate                 = New-Object system.Windows.Forms.Label
$LB_StatusUpdate.AutoSize        = $true
$LB_StatusUpdate.width           = 25
$LB_StatusUpdate.height          = 10
$LB_StatusUpdate.location        = New-Object System.Drawing.Point(85,113)
$LB_StatusUpdate.Font            = 'Microsoft Sans Serif,10'

$Form.controls.AddRange(@($TB_ComputerName,$LB_ComputerName,$TB_UserName,$LB_UserName,$LB_INFO,$LB_TITLE,$BTN_RUN,$BTN_SAVE,$BTN_Cancel,$LB_Status,$LB_StatusUpdate))

$BTN_Cancel.Add_Click({ closeForm })
$BTN_SAVE.Add_Click({ saveImage })
$BTN_RUN.Add_Click({ RunCalculation })

#Write your logic code here
Add-Type -AssemblyName System.Windows.Forms.DataVisualization
$Chart = New-Object -TypeName System.Windows.Forms.DataVisualization.Charting.Chart
$Chart.Size = '750,600'

$ChartArea = New-Object -TypeName System.Windows.Forms.DataVisualization.Charting.ChartArea
$ChartArea.AxisX.Title = 'Directory'
$ChartArea.AxisY.Title = 'SizeGB'
$ChartArea.AxisX.Interval = '1'
$ChartArea.AxisY.Interval = '5'
$ChartArea.AxisX.LabelStyle.Enabled = $true
$ChartArea.AxisX.LabelStyle.Angle = 90
$Chart.ChartAreas.Add($ChartArea)
$Chart.Series.Add('SizeGB')
$Chart.Series['SizeGB'].ChartType = [System.Windows.Forms.DataVisualization.Charting.SeriesChartType]::StackedBar
#$Chart.Series['SizeGB'].IsValueShownAsLabel = $true

$Title = New-Object -TypeName System.Windows.Forms.DataVisualization.Charting.Title
$Chart.Titles.Add($Title)
$Chart.Titles[0].Text = 'Folder Size Analyzer'

function closeForm { $Form.close() }

function saveImage {
    if(!$Chart.Series.Points) {
        $LB_StatusUpdate.Text = "Run the report first..."
    }
    else {
        $SaveChooser = New-Object -Typename System.Windows.Forms.SaveFileDialog
        $SaveChooser.ShowDialog()
        $Save_Filename = $SaveChooser.Filename
        $LB_StatusUpdate.Text = "$Save_Filename\DirectorySizeChart.png"
        $Chart.SaveImage("$Save_Filename\DirectorySizeChart.png", "PNG")
    }
}

function RunCalculation {
    $computer = $TB_ComputerName.Text
    $user = $TB_UserName.Text
    $LB_StatusUpdate.Text = "Running disk space query on \\$computer\c$\users\$user..."
    Start-Sleep 3
    $LB_StatusUpdate.Text = "Do not close this window before you see the chart below!"
    Start-Sleep 3
    $output = get-childitem -force "\\$computer\c$\users\$user" -ErrorAction SilentlyContinue | where-object { $_ -is [io.directoryinfo] } |
        foreach-object {
            $len = 0
            get-childitem -recurse -force $_.FullName -ErrorAction SilentlyContinue | foreach-object { $len += $_.length }
            [pscustomobject]@{
                Name = $_.FullName
                SizeGB = [math]::round($len / 1Gb, 2)
            }
        }
    
        $output | sort-object SizeGB | foreach-object {
            $Value = $Chart.Series['SizeGB'].Points.AddXY($_.Name,$_.SizeGB)
            $LB_StatusUpdate.Text = "Report created..."
        }
    
    $Chart.Series.Points | ForEach-Object {
        if($_.YValue -eq 0) { $_.IsValueShownAsLabel = $false }
    }
    $Chart.Left = 20
    $Chart.Top = 240
    $Chart.Anchor = [System.Windows.Forms.AnchorStyles]::Right -bor [System.Windows.Forms.AnchorStyles]::Left -bor
    $Form.controls.add($Chart) 
}

$Form.Add_Shown({ $Form.Activate() }) 
$result = $Form.ShowDialog()

if ($result -eq [System.Windows.Forms.DialogResult]::Cancel)
{
    write-output 'User pressed cancel'
}

need help with 2 things:

1. how can i transform the whole calculation stuff into a start-job, so it doesnt crash the form? line 153-162
2. how can i show only the values of the datapoints that actually have a yvalue. the way in line 168 is not working :(