Check AD User Replication with while and foreach

Hello scripting experts

I'm not a powershell specialist . I had built a script that create an ad-user and give them permissions to a folder with set-acl. With set-acl i can't set a specific domain Controller so i had the problem when the user that i have just created is not replicated to all AD controllers. So i will check this in the script and wait until the user is replicated. I try this but it doesn't work. What do i wrong?

Import-Module ActiveDirectory 
$DCs = get-addomain 
# test list all DC -// write-host $DCs.ReplicaDirectoryServers 
foreach ($objitem in $DCs.ReplicaDirectoryServers)
{
write-host 'check on' $objitem
    while ($Aduser_CHK -ne $NULL)
    {
    $Aduser_CHK = (Get-ADUser -Identity thoflo -server $objitem).ObjectClass
    trap {'User do not exist on all DCs' -f $_.Exception.Message;    continue}
    Start-Sleep -Seconds 1
    }
}

Thank you for all replies

Florian