add a customized field to the Cust. ledger entries table after posting

I am trying to add a customized field e.g commission % into the cust.Ledger entry for all invoice posted.
Here is what I have done.
1. Created a field on the Sales Line table, GenJnlLine , and Cust.Ledger Entry Tables

so I need to know how to add my code from the sales Line into the GenjnLine so that it can populate the Cust.Ledger entry table.

Please i require your assistance