HELP! New Guy Trying To Use SQL Server Express With ADP For Reports And Forms

Please forgive my ignorance here. I'm reading as many of the For Dummy and IDIOT's guides as I can. So far, I must brag and say, I've done fairly well. (For a beginner)

Hopefully, this is an easy problem to fix, or at least to explain where I'm going wrong. This is as stripped out as I can make it:

- Using Access Database Project files to provide forms and reports for Customer Service Reps over a Windows network while using SQL Server 2005 Express as my engine.
- I am using a simple combo box in the Access form to allow CSRs to type in a job number and therefore find and fill in related info to the visible fields.
- This used to work when Jet was my database engine. Now, I receive an error, stating "The expression After Update you entered as the event property setting produced the following error: Error accessing file. Network connection may have been lost.
In asterks it says, The expresion may not result in the name of a macro, the name of a user-defined function, or [Event Procedure]. There may have been an error evaluationg the function, event, or macro.

I don't care how I get it done, I just want this simple feature to work again, so my CSRs will quit hounding me.
PLEASE HELP! Keep in mind, I don't know Visual Basic or T-SQL very well.

THANKS!!

DAVID