can you rewrite an error message easily?

heres the scenario:

forms text box, links to the DB which has a setting of "short date" therefore, if the user puts any format other than this 00/11/0000, it of course whinges with error 13 "type mismatch"

Can I re-write this error so that when it pops up the user will see rather than run time error something like "Check your date format"?

other than that, I dont know how to write into the program "the Database requires you to put the date into the dd/mm/yyyy format" sort of thing...

any ideas?