I've managed to get this code running on a fairly basic database.

What's annoying me is that it falls over so easily. I share Irprogram's problem of not being able to get this to work with text boxes and combo boxes simultaneously, I cannot get the code for this functionality (supplied in the article) to run. The other issue I'm having which seems a bit odd is that it throws up an error message when a date field is changed (Error 3251 again). The date field on the form is just a text box, so why doesn't the formula just treat it as text?