Limit Date Values to Quarters

I have a field that shows dates as quarters. Right now it is just a date/time field, but that posses a problem, as the user can enter any date possible. I want the dates to be limited to March, June, September and December, and any year they choose. Can someone please help me with this. I tried fooling around with the input mask and the validation, but I just couldn't figure it out.

Thanks in advance

In simple English it seems that you condition is

Month(DateEntered) must be 3,6,9 or 12

since March is 3, June is 6, September is 9 and December is 12

You could probably check for this before you update the table and take appropriate action.

Good luck.