Validation Suggestions?

I'm looking for a good solution for this validation scenario. I've created a time tracking application and I want to do two things. When a person puts in an amount, I want to make sure that it's numeric and that it is entered in quarter of hours. So, something like 1.25, 1.5, 1.75, 2. I'm trying to decide how best to do this. Would a function that rounds to a quarter hour be best? Or would some sort of regular expression that looks for a format be better? Any suggestions are welcome.

Thanks

Andre

Try out the following link which will give you some idea in creating the regular expression:

http://regexlib.com/Search.aspx?k=quarter