Automate an issue for a substitue item on parts list

Wanted to find out if anyone has ideas the best way to automate a substituted part on a work order parts list.

Here is the scenario:

Item A on parts list calls for a quantity of 12.  But, we don't have item A and can use a substitute item B.  And, we only have 3 of item B ready now.

The operator will go to the work order and then go into the parts list.  They will find item A on the parts list and then go to row exit and select substitute item.  A new screen pops up and operator enters quantity 3 for item B on this screen.