How to call TAB on unit price update for non-project transactions?

Summary:

Not able to figure out how to call TAB and set an asset clearing or expense account based on a line price TAB source when not using PPM.

The "Rebuild" would work but the UI seems to clear the charge account before TAB is called. Which means that any update the buyer has done manually will be wiped out. So looking for options to call TAB automatically when the unit price is updated, the unit price would be best of course, but alternate suggestions are also welcome, of course.

Content (required):

We have some units working without PPM, and for them, we have not figured out a way to correctly drive the natural account based on a line price TAB source when the unit price is updated, e.g. in a change order. Which we need to do to drive the correct asset clearing or expense account. We thought we could use the "Rebuild Account" option, but it seems it starts with wiping off the charge account before TAB is called. Meaning all updates by buyers, which we will do manually for all GL segments except the account, are gone.