>>What do you use as RowSource? Actually you have to change something there (filter for table or new contain for cursor...) and then Requery.
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>When I tested this on a local basis, every thing were fine, but on the net with real data, the thermometer, were displayed, the combo lost the focus, and then get it again after the thermometer disapear, the combo requeries and . . . infinite loop

Requiry second combo in Valid event of first combo shouldn't yield this problem. May be you call query from another place. Again, what is RowSource for your combo?