Update Commission Details?

We have a scenario where the salesman and/or commission rates can change between the time the order was entered and when it runs through sales update.  Is there any way to have this info updated, besides manually going in to the sales order and making the changes? 

We are looking at writing a custom UBE that will run across open orders and make any necessary updates, but I thought I would check to see if anyone else has come across this issue and has implemented a different solution. 

Any info would be most appreciated.

Thanks!