Some different parameter types and values for demonstration purposes

ParameterOptionsDemo.ps1

$scrpt1 = { 
    if(!(test-connection 'localhost' -Count 1 -Quiet)){return}
    else{0..7 | % { "'"+(get-date).AddDays($_)+"'" }} 
}
$scrpt2 = { 
    if((get-date).minute % 2 -eq 0){
        @('Mon','Wed','Fri')}
    else{
        @('Tue','Thu','Sat')
    } 
}

Register-ArgumentCompleter -CommandName MyTest -ParameterName AListOfthings -ScriptBlock $scrpt1

Register-ArgumentCompleter -CommandName MyTest -ParameterName Day -ScriptBlock $scrpt2

function mytest {
    param(
        [switch]$yes, # for when yes/no , true/false are all that is needed
        [parameter()]
        [validaterange(500gb,20tb)] # validate Min and Max values for param
        [int64]$DiskSize = 16tb, # provide default for param if no value is provided
        [datetime]$AListOfthings,
        [string]$Day
    )
    cls
    "AListOfThings values was provided by the Register-ArgumentCompleter"

    "The $Day parameter had values like $Day available at run time based on a condition"

    if ($yes) {
        'You supplied the $Yes parameter'
    } else {
        'You did not supply the $Yes parameter'
    }
    "Disk size was {0}, {1:N2}GB, {2:N2}TB" -f $DiskSize, ($DiskSize/1gb), ($DiskSize / 1tB) | write-host
}


mytest   -disksize (43980465111040/3) 

mytest   -disksize (43980465111040/3) -Day Wed