Not sure how to do this, I'm trying to validate a form, I've got all the form stuff working, but I have 2 fields: StartTime and EndTime, and they're comboboxes, with the same lists of about 20 entries : 7:00 AM to 5:00 PM in 30 minute intervals

I'm trying to make sure that someone doesn't accidentally enter an EndTime that's before the StartTime, but I'm not exactly sure how to compare these two fields. (if EndTime < StartTime)

Any help is greatly appreciated, thanks!