There are a couple of concepts to consider
1, Split your database into a FrontEnd (holds everything except the
tables) and a BackEnd which holds just the tables. You get there by
making a copy of your application and call the first copy *GUI.mdb
(FE) and call the 2nd copy *DAT.mdb.
2. Put *DAT.mdb in a folder visible to both users on the LAN.
In *GUI.mdb, go to Tools | AddIns | Linked Table Manager and link to
the tables in *DAT.mdb - out there on the server where you just put
it.
Now give a copy of *GUI.mdb to each person who might want to enter or
see the data. Hot dang, you're doing multi-user stuff!
You can continue developing in a copy of *GUI.mdb and each time you're
satisfied with the level of changes and you've debugged them, once
again link to the real data out there on the server. Now email a
message to all of your users telling them to rename or delete their
current version of *GUI and replace it with the copy of the newer,
better version attached.
HTH