PS - Update Kalendereintrag via EWS

function Unix_autoFBR {
    param(
        [Parameter(Mandatory=$true)]
        [string] $UNIXFBID
    )

    $itemId = $UNIXFBID

    write-host "----------------$UNIXFBID----------------"  

    $appointment = [Microsoft.Exchange.WebServices.Data.Appointment]::Bind($service, [Microsoft.Exchange.WebServices.Data.ItemId]::new($itemId))

    $category = "FBRelevant"  
    $appointment.Categories.Add($category)
    $updateOptions = [Microsoft.Exchange.WebServices.Data.SendInvitationsOrCancellationsMode]::SendToNone
    $appointment.Update([Microsoft.Exchange.WebServices.Data.ConflictResolutionMode]::AlwaysOverwrite)
}