Use of GetLoggedInWindowsUserID

I'm trying to capture the Rename File event in EPDM 2010 and then getting the UserID of the person doing the rename.  I'm using this VB.Net code:

    Public Sub OnCmd(ByRef poCmd As EdmCmd, ByRef ppoData As System.Array) Implements IEdmAddIn5.OnCmd

        If poCmd.meCmdType = EdmCmdType.EdmCmd_PreRename Then

            Dim vault As IEdmVault11 = poCmd.mpoVault

            For Each cmdDatum As EdmCmdData In ppoData

                ‘...

                Dim id As Integer = vault.GetLoggedInWindowsUserID(vault.Name)

                ‘...

But the code bombs because of the call to GetLoggedInWindowsUserID.  (If I comment this line out, it runs fine.)  The error I get is:

We are not using Windows to manage our logins, we are using Enterprise PDM logins.

Am I calling this wrong?  Any other ideas?  Thanks!

SolidworksSolidworks Pdm enterprise Pdm