Code help please

Hi Guys...I am a newbee to ABAP and need some coding help

I am trying to write a small user exit that will copy field XREF1 from one document and insert it into the XREF1 field of the new document.

I am trying to use structure rfops_dk in my code. Transaction F-04 uses this structure to populate data with and I have to see if the user selected a certain document that has XREF1 in it, to copy it to the new XREF1 field.

thanks so much

Brian