Running an advanced modify for a transaction line action only in the context of the modified line

Summary:

Our customer business process requires the creation of a lot of different transaction lines. They can edit a particular line by clicking on the part number of that line and accesing the "details page" for that particular line. They can then save the changes to that specific line.

Content (please ensure you mask any confidential information):

We need to perform certain calculations once the saveChanges_l action is clicked by our customer, but for both clarity and performance issues we would like to have those calculations executed ONLY on the transaction line our customer is modifying.

Our problem is that when we add transaction line attributes to our advanced modify, we can't reference them directly without iterating through the whole transaction lines, and we seemingly have no way to access only the fields that belong to the current line, or the _