There is a problem using the valid in a grid that apparently has not been corrected in 6 either. Below is a MS article with a proposed work around:
BUG: GotFocus & Valid Events Fire Unexpectedly in Box of Grid

>Do you know why when you return .F. within a valid method of textbox in a grid it lose the focus anyway if you click on another object.
>
>Note: the Textbox control work fine if it's not in a grid
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>All idea or suggestion will appreciate
>Thank's in advance