MessageBox.ps1

# No title
[System.Windows.Forms.MessageBox]::Show("We are proceeding with next step.")

# With title
[System.Windows.Forms.MessageBox]::Show("We are proceeding with next step." , "Status")

# Yes/No
$result = [System.Windows.Forms.MessageBox]::Show('Do you wish to continue', 'Warning', 'YesNo', 'Warning')
if ($result -eq 'Yes') {
  # do something
}