No guarantees but here's what I'd try:

Edit the Nominal Activity report and go to Report / Joins.  This shows which tables are currently used and accessible within the report.  Add the Audit_Split table by dragging from the list on the left and dump it anywhere on the main pane. 

Then link it to the audit_journal table to make sure that it picks up the right data.  To do this, drag open the field lists of each table and scroll so you can see Split_number in both the Audit_Journal and Audit_Split. Put your mouse over Split_Number in the Audit_Journal list (important to do it this way round) and drag it onto Split_number in the Audit_Split table.  You should see a yellow key against the Audit_Journal and and infinity sign against the Audit_Split table. 

You should now be able to go back to your layout and add the field you want from the Audit_Split table.  Test, test, test!

Thanks Anita!

Thanks Anita!