InfoPath Dev

I have a text box in my infopath, i want to restrict users to enter any numbers or special characters. another text box has to accept only positive numbers between 0 to 31(this is actuallay days in a month).Please guide if anyone knows how to achieve it.

Hi - I'd use validation for this. I've attached a sample. Save it locally, right click and open in design and from there you can preview and see how it works.