Auto format textbox to time

We have some hourly employees who need to fill in time sheets and they sometimes have problems with the math so I'm developing an application to help with that, their pay period is every two weeks. So what I have here is a basic time in and time out sheet where they can enter the times for their shift. I was wanting it to auto format so that if they enter 330 (like below) it will show as 3:30, also if they enter a leading 0 on a time such as 0220, (like below) I would like it to show as 2:20. Can anyone help with that? I'm using visual studio 2012 asp.net.


Attachment 32389

Use the phone format. Drop-down HOURS and then 4 MINUTE choices for each. Or, even better, just SHIFT, OT, and then OT HOURS/MIN

I was thinking about using drop down boxes for the hours, that would eliminate the am/pm drop down, but I was able to come up with code that could figure out the time difference without specifying am/pm or using a 24 hour clock. Anyway, I would like the user interface to be as friendly and clutter free as possible and having separate drop down boxes for time and minutes will double the amount of textboxes.

I think idiot-proof would be better. In the long run, anyways. Military time isn't that hard. And PC's compute date/time