>Thank's Sergey, that works just fine ! I just noticed that the form I used to do the testing was subclassed. When I did the test with the original vfp form and textbox I did not have the problem, but I can't find anything in the class that could be the cause of the problem. Anyhow, like I said, your solution works. Thank's a lot !

It's a bug you can see even on a fresh form with textbox Format="!". Another workaround would be to use Inputmask = "!!!!!!!!!!!!!!!!!!!" instead of Format.