Alter Report Sort in Crystal

My customer wants to alter the Accounts Receivable Aged Invoice Report to sort on the Salesperson number listed in the AR_CUSTOMER (name sp?) table rather than the salesperson number in the AR_AgedInvoiceRportWrk table which is the same number that is in the salesperson number that shows listed on the invoice rather than the customer master.

I added a User Defined Field and added the salesperson number from the AR_CUSTOMER table to the WRK table. 

I then changed the Group Header AND the @Salesperson formula to point to the UDF I set-up.

But the report still sorts by the original salesperson number listed in the WRK table and not the UDF field.

What am I missing?