Modify an existing RTF Template using BI Publisher

I  have been tasked with modification to an existing RTF template used for printing checks out of Oracle Payables.  We have, of course, modified this template (probably from seeded templates) to conform to the checks we issue here.  For refund checks I have been asked to modify the check stub and ADD an additional field.  I know how to do this with BI Publisher, as I have modified RTF Templates that have been created using this tool.  However, this one was not created using BI Publisher. I need the data defination file for this template but no clue how to