Fax number need to populate automatically in delivery VL02N

Hi gurus,

I got struck up in a issue.I need to populate the fax number for delivery(VL02N).Now its picking up wrong fax number.All i did is, i checked in the NACE tcode and put a break point in the driver program.When i create an output type and click on communication, its not triggering my program.I need to debug my code and do some changes.Please tell me the exact way to debug my code.