If you already have it in TBC, don’t bother messing with it in Access.
Because TBC allows for multiple reorientations within the same setup, you will have to change the backsight observation itself to point at the correct number for each Backbearing. The “Backbearing” object is only there to log/set the base horizontal circle for the observations contained within it.
So just expand any Backbearing objects and find the backsight observations (look the same as other obs, but have the little target behind them).
Select the backsight observations and modify the point number shown in the Properties. When it asks you to merge, say yes:
Recompute and any sideshots tied to that Backbearing will be fixed. Repeat for any other Backbearings in the setup.
Just be aware that since Rounds are stored separately from Backbearings (since they are not sideshots and have their own starting orientation so that they can be analyzed separately in a network adjustment) if you have any Rounds to the backsight in that setup you will have to modify the Sets separately as well:
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman