SAP Business One Automatic Row numbering for Matrix

I am making an add-on for SAP B1 8.82. I would like automatic row numbering for my matrix column "#" i.e. UID "V_-1". Is there a feature in 8.82 that can help me do this? I am using UserDataSource for my matrix. How do I get to have row numbers that automatically update when I add/remove a row? I want to add code to menu event 1292 for adding row numbers manually and menu event 1293 for deletion. Any help appreciated.