masked textbox "1-9999999"

I am trying to implement a mask on a textbox that forces the user to follow the format "1-9999999", where the "1-" will always be at the beginning, and they can only enter 7 numbers after that.  I added the masked edit extender, along with the script manager, and put the mask "1-9999999", but it isn't recognizing it at all.  Do master pages affect using the ajax control toolkit? thanks