Problem mit Powershell Backup-Skript

# [content:309121#1114968]

function CopyFolder($source, $dest) {
[void] [System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms")  
	write-host "CopyFolder(${source},${dest})" -F Green  
	$Logfile     = "c:\temp\backup-usb-stick-$(get-date -f yyyy-MM-dd_hh-mm-ss).txt"  
	Robocopy $source $dest /MIR /TEE /R:2 /LOG:$Logfile | Out-Null
	[Windows.Forms.MessageBox]::Show("Die Dateien wurden von ${source} nach ${dest} gesichert.", "Sicherung", [Windows.Forms.MessageBoxButtons]::OK, [Windows.Forms.MessageBoxIcon]::Information)   
} 

Get-EventSubscriber | Unregister-Event -Force
Register-WmiEvent -Query "Select * From __InstanceCreationEvent Within 1 where TargetInstance isa 'Win32_LogicalDisk' and TargetInstance.DriveType = 2" -SourceIdentifier 'RemovableDetector' -Action {  
	Get-EventSubscriber | Unregister-Event -Force
	
	$name = $Event.SourceEventArgs.NewEvent.TargetInstance.VolumeName
	$drive = $Event.SourceEventArgs.NewEvent.TargetInstance.DeviceID
	
	write-host "Wechselmedium '${name}' erkannt." -F Green  
	
	$volume = "USB STICK"  
	$target = "C:\Backup-USB_STICK"  
	if ($name -eq $volume) {
		write-host "Dateien von ${drive} nach ${target} kopieren ..." -F Green  
		CopyFolder $drive $target
	}
} | out-null
cls
write-host "Warten auf Wechselmedium ..." -F Green  
while($true){sleep 1}

write-host "Dateien von ${drive} nach ${target} kopieren ..." -F Green  

Warten auf Wechselmedium ...
Wechselmedium 'USB STICK' erkannt.  
Dateien von D: nach C:\Backup-USB_STICK kopieren ...