Autogenerating Numbers For A Primary Key Field, StudyId, In A Table--but With A Few Twists.

I have a question on autogenerating numbers for a primary key field, "studyID," in a table��but with a few twists.


We want studyID to be automatically generated as a 5-digit number. Additionally, we have two study sites and would like the studyIDs pertaining to the first site to begin with a 1 and StudyIDs associated with our second site to start with a 2. When we begin entering data, we will enter either a 1 or 2 in a field called, "Site." Upon entering that 1 or 2, we would like at that moment for Access to instantly autogenerate the appropriate studyID for that site and put it in the "StudyID" field. We want the very first number generated for each site to end in a 1 (10001 and 20001).


Here��s the range of values we want our StudyIDs to be (this is to be our validation rule as well):


10001-19999 for Site 1

20001-29999 for Site 2


Your suggestions are VERY VERY WELCOME! THANKS!