Apologies if this has been answered before. I did a search and looked at loads of posts but apart from a hint, I didn't get the answer to my question. I have never actually needed to teach input masks in Access before (and they haven't worked on our network until recently anyway). Now they've put it on the AQA Business & Communication Systems spec so I'm teaching it to my year 11s. I thought I'd try it with postcodes, as they seem the obvious choice, but can't get it to work properly. The problem is that the number of letters and numbers in the first half of the postcode varies. You can have either one or two letters followed by either one or two numbers. I tried this: L?90 0LL but it only works if you then enter a space for the missing letter or number. Can anyone tell me how to do it so that it works for any valid UK postcode without having to put in spaces? I'm using Office 2003, if that makes any difference. If it's not possible to make it work with postcodes, what other simple example would you use to teach it to a mixed ability group of year 11s? I thought forms (ie registration groups) but that won't work either because of them having either 1 or 2 digits.