Trimble Access, how to assign elevation to previous shots

I setup instrument on point "A", enter height, do the setup, start topo shots with rod height, then at the end I forget to take a shot to my BM. I move to point "B" which of course has no elevation, then do the setup with backsight as "A", Now i take a shot to BM and all my points from now on have elevations, INCLUDING point "A", is there anyway to manipulate the job file ( on the data collector, or later on PC) so that all the previous shots taken from Station "A" get their elevations based on BM?