The reason I asked is that I ran into a similar behavior putting a combo box in a grid - it didn't respect the ControlSource I specified, but used the next unused field in the grid RecordSource. To cheat around it, I had to put a blank unused field of the proper data type in my table. What you may be seeing is a reference to something different from your intended data source. I don't know what to do about it, but I'm betting it could be trouble later.