I don't have VB handy so....

Set the KeyAscii to true on the form level (when it loads help file tells you how) and in the keydown event check for chr(13) if it is true then
[VBA]

textbox.text = Format(textbox.text,"##,###")
sendkeys "{tab}"

[/VBA]I will post the correct code tonight when I get home. You could try till then to code it, use F1 a lot (I do).