Fetching an autonumber on a form.

[Missionary]

I have two tables. Basically there is one [tblReq] that has location [Tag], project [Service] and an autonumber [ID] The other table [tblLog] stores a cheklist record for every time that project gets inspected. It has a number field that is linked to the Autonumber from tblReq and the date and some other things.
Now in my Log form, I want to be able to look up the Tag and the Service in combo boxes and have the form automatically input the ID into the number field in tblLog.

What I've got so far:
I first made a query with all the values and a form that showed them, but instead of bringing up the ID, it just created a new record in tblReq with a new Autonumber.

Then I tried makeing a subform, but I can't figure it out.
This seems like something people would do alot, but I couldn't find anything on the forums. I probably just don't know where to look.

Thank you.

[NeoPa]

I'm sure we can find a solution, but could you lay out the tables for me so I can think the problem through more clearly.

This will work better if you can post the meta-data (info about the layout / structure) of the table in the same way as I use in my example. Click on the Reply button and you will have access to all the codes I've used. PK & FK stand for Primary Key & Foreign Key respectively.
Table Name=[tblStudent]

Field; Type; IndexInfo
StudentID; AutoNumber; PK
Family; String; FK
Name; String
University; String; FK
Mark; Numeric
LastAttendance; Date/Time