Below you’ll find a slight modification to a post from Mike Pfeiffer on querying Exchange 2010 CAS servers to obtain the current count of OWA and RPC clients.
function Get-CASActiveUsers { [CmdletBinding()] param( [Parameter(Position=0, ValueFromPipelineByPropertyName=$true, Mandatory=$true)] [String[]]$Name ) process { $Name | %{ $RPC = Get-Counter "\MSExchange RpcClientAccess\User Count" -ComputerName $_ $OWA = Get-Counter "\MSExchange OWA\Current Unique Users" -ComputerName $_ New-Object PSObject -Property @{ Server = $_ "RPC Client Access" = $RPC.CounterSamples[0].CookedValue "Outlook Web App" = $OWA.CounterSamples[0].CookedValue } } } } Get-CASActiveUsers CAS-1,CAS-2,CAS-3