Hi
You don't give much to go on but assuming your tables are properly normalised you can either set up update queries and call them from VBA code on a command button or else you could use ADO to manipulate various recordsets based upon criteria from your form.
If you need batch updates then probably best with queries.
If more subtle updates or very specific things then ADO might be better.
I realise this just points you but without more info its hard to see where to start. A bit like how long is a piece of string!
Anyway hope this is a helpful starter.
Good luck!