Xpath expression for idoc fields

Hi,

I have a scenario to invoke 2 different operation maps based on a date condition in the incoming idoc. I have tried setting up an XPATH condition in the interface determination similar to INVOIC02/IDOC/E1EDK03/[IDDAT = 13 and DATUM > 2013-05-01] to pick OP map A and another condition INVOIC02/IDOC/E1EDK03/[IDDAT = 13 and DATUM < 2013-05-01] to pick OP MAP B.

But during runtime, I am able to get only OP Map A picked even if the DATUM in the Idoc is less than 2013-05-01. Am I missing something ?? I even tried using paranthesis like INVOIC02/IDOC/E1EDK03/[(IDDAT = 13) and (DATUM > 2013-05-01)] but that doesnt seem to help.

Any help is appreciated.

Teresa