Yeah ok, the point is you have to go through "Get-VM" first...

You can't simply "Move-HardDisk" like this:

$hdsrc = Get-HardDisk -Datastore $srcds

foreach ($hd in $hdsrc) {

  Move-HardDisk $hd -Datastore $dstds

  ...

Because then it will tell you that the disk is locked.