// JavaScript Document

	var p;
		
		function next(i) {
			return function() {
				//strip non-digits
				p[i].value=p[i].value.replace(/[^0-9]/g, "");
				
				//go forward one box when full, except when on the end box
				if(p[i].value.length==p[i].size && i<p.length) p[i+1].focus();
			}
		}

		function back(i) {
			return function(e) {
				//go backward one when empty, except when on the first box
				if(e.keyCode==8 && p[i].value.length==0 && i>0) p[i-1].focus();
			}
		}

		window.onload=function() {
			p=document.getElementById("phones").getElementsByTagName("input");

			for(var i=0; i<p.length; i++) {
				p[i].onkeyup=next(i);
				p[i].onkeydown=back(i);
			}
		}