>>May be it's a problem in VFP8 version I'm using, but I can not change the number by typing it in the text portion. It only allows me to type one digit instead of the number.
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>I have no problems with VFP8 also, of course this code will change color at every single keystroke.

BTW, does Keyboard input works correctly for you? I can enter any number outside the range and get an error, of course. What's the purpose of KeyboardLowVal/HighVal then?