OnUnSetFocus ?

I'm trying to find a trigger that will tell me when the user has changed focus off of a textfield. In other words, when they click on it and fill it out then move on to the next field, I want to check that information as soon as their keyboard changes focus off of that textfield. Is there any way to do that?

I figured I could just check when they hit the next textfield in line, but their is no telling what order someone might fill it in. Thanks for the help.

webG