Very cool :D Thanks, Dave!
Bonus: This solved another problem I was having for a textbox element as well that I wanted to restrict to either leaving blank or integers between 0 and 75.
Also just to note in the help file under mask attribute the following link requires a login:
"For example, see http://utilitymill.com/utility/Regex_For_Range for a tool that generates expressions constraining input to a range of integer values."