function phoneNumberCheck(fieldname){
var numb = "0123456789";
//var alpha = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ ";

var w = "";
for (i=0; i < fieldname.value.length; i++) {
x = fieldname.value.charAt(i);
if (numb.indexOf(x,0) != -1)
w += x;
}
fieldname.value = w;
}