Validate free space on destination datastore

Hi,

Please help me, how can I validate the free space on the destination datastore before I start the storage vmotion on the VM

$source = "DS03"

$destin = "DS39"

Get-Datastore $source | Get-VM -PipelineVariable vm |

ForEach-Object -Process {

   $task = Move-VM -VM $vm -Datastore $destin -RunAsync

   while ($task.PercentComplete -ne 100)

   {

  sleep 5

   $task = Get-Task -Id $task.Id

   $sProg = @{

     Activity = "$vm Storage vMotion from $source to $destin"

     Status = "$($task.PercentComplete)%"

     PercentComplete = ([int]($task.PercentComplete))

   }

   Write-Progress @sProg

   }

}