Hey, Mindy,
As Rod said, you'd want to implement this behavior in your base textbox class. The logic would need to evaluate the length of what's entered against some custom property for an input mask, defined length, etc.
I haven't seen any specific equivalent of SET CONFIRM either. This is perhaps a stretch, but you may want to check out this C# MaskedEdit Control from the Code Project. I used it a while back and it's pretty nice. (You need to register to download things, but it's free).
http://www.codeproject.com/cs/miscctrl/maskededit.aspI don't know if this has the equivalent of SET CONFIRM, but it may contain other capabilities that might make it easier to implement a SET CONFIRM, as opposed to building it from scratch.
Hope that helps...
Kevin
