Subform filter fails

[LongWayFromHome]

My filter in a called procedure results in a Null for the record, but I can't
see why. The calling procedure is on the main form, SWB, and the called
procedure is in a utility module. The subform, EndwmtSubFrm, should go to
the specified record, but doesn't. EndwID is a string, and it does pass
correctly from the calling procedure.

Would appreciate any advice on where the problem might be.

Public Sub SetEndwmt(EndwID)
With Forms!SWB!EndwmtSubFrm.Form
.Filter = "EnFNo = '" & EndwID & "'"
.FilterOn = True

Thanks!