Print UDF in repetitive area and relate it to another table

I have created a UDF in Marketing Docs (A/R Inv - Rows). I need to print the value on the UDF and relate it to CardCode in OCRD to subsequently display the CardName in the repetitive area on the A/R Invoice.

I can print the UDF OK. When I add Text fields with source Database from Table OCRD, the entire repetitive area no longer prints.

Any ideas?