Sychronizing forms

[Joe]

I have a database with 2 forms used for entering data
about a utility into one database. The problem is that
when I switch between them the specific record that I am
trying to update does not continue over. I have tried to
use the expression builder on the field that is on both
forms and it hasn't worked so far. The field is an
autonumber long integer value. Can anyone provide an
example of the syntax or let me know if I'm putting it in
the wrong place, I have used the before update and control
source properties and just seem to be doing something
wrong.

Any suggestions on doing this in VB would be great also.

Thanks, Joe