OK So with the help of this community and especially a veteran user pipeline, I've been clued in to a suitable method for doing exactly what I wanted.

Specifically I had a piano part that I didn't like a single measure that BIAB generated and I wanted to instruct it to re generate that single measure.

(the solution would also work for several measures.)

The following is a step by step.

Click Edit and then go down to "copy special" and click "copy/move tracks
(on mine system thew window takes a while to open) see diagram 1.

choose the source and destination tracks

Click OK

In my case the Piano track has been copied to Utility 1

Click on the Utility 1 track
Click “Audio” then click “audio edit”

This opens the Audio Edit window as in Diagram 2 and displays the audio on Utility 1

Click the checkbox for “snap” and highlight the measure you want to regenerate
(in my case measure 3)

right click on Utility 1 track and highlight generate and then click on “select and generate real tracks”

The style window opens

Select the real track that matches the track you're replacing

Click OK

BIAB now regenerates the piano for measure 3 only

Done

Attached Files (Click to download or enlarge) (Only available when you are logged in)
Capture 1.PNG (11.63 KB, 55 downloads)
Diagram 1
Capture 2.PNG (147.7 KB, 55 downloads)
Diagram 2