Put this code in the change event..
// restrict entry to digits and a dash
if (xfa.event.change.match(/[0-9\/]/) == null)
xfa.event.change = "";
//restrict the input to 10 characters
if(xfa.event.newText.length >10)xfa.event.change = "";
// Allow the slash at the 3rd and 6th character
if (xfa.event.selEnd == 1 || xfa.event.selEnd == 4)
xfa.event.change = xfa.event.change + "/";
Thanks
Srini