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>A typo. Either in one of the controlsource values ie thisfrm.property or possibly an error in one of the Refresh() methods.

David,

You were right - a typo. I'm always amazed how I can spend a half hour looking for the cause of an error, post a message here, and then two minutes later. even before receiving any replies, I'll take one last stab at it and find the mistake that caused the problem. Thanks anyway.