Shani,
I have Acc 2010 and tried something I found online. Apparently this was available in 2007 according to the post I saw.
You can add a CHECK constraint in Access, but you must do it directly in code. You can not use the query designer.
I took a sample table in my database and added the Check constraint with this code entered directly in the immediate window.
Code:
CurrentProject.Connection.Execute "ALTER TABLE CityTbl ADD CONSTRAINT CheckSt3 CHECK(State IN ('Texas', 'Michigan'))"
I tried adding a record for Oswego , New York and got the attached message.
So the constraint was added and works as expected.
Good luck with your project.