restricting user exit ZXEDFU02 to one customer in WE20

I'm new to SAP. I've just written a code in user exit 002 (include zxedfu02) for the bill-to party invoice IDOC generation (FUNCTION IDOC_OUTPUT_INVOIC). My code is working perfectly. The only problem is I would like to restrict the use of this user exit to only one of my customers. From my understanding once I've programmed the user exit, every IDOC that is generated using IDOC_OUTPUT_INVOIC will perform my user exit, however I would like to be only executed for one partner. How do I do this?

If possible, please post a step by step solution to my problem, I would really appreciate your help.

Thanks in advance.

Edited by: mrisad on Jul 29, 2010 4:21 PM