function checkNum(field,thevalue,valid) {
	var ok = "yes";
	var temp;
	for (var i=0; i<field.value.length; i++) {
		temp = "" + field.value.substring(i, i+1);
		if (valid.indexOf(temp) == "-1") ok = "no";
	}
	if (ok == "no") {
		alert("Invalid entry (numbers only)");
		field.value = thevalue;
		field.focus();
		field.select();
   }
}