Updating back end DB question

What happens if I update a back end database while users are in the front end
in Access 2003? Will the data being entered at the time be compromised?

Basically, the front end has the forms and a table that contains the data
entry info. The back end consists of a series of tables that contain
pre-existing background info on the possible data entries in the front end
table.

In other words, I'm wanting to update the background tables periodically
(perhaps even daily), in preparation for users' data entry, but without
having to ask them to exit the front end database every time.

Any help?!?! THANKS!!!!
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GD