phone no validation

function validatePhone(obj,msg)
{
var validNum =/^[\(]?(\d{0,3})[\)]?[\s]?[\-]?(\d{3})[\s]?[\-]?(\d{4})[\s]?[x]?(\d*)$/;
if (validNum.test(obj.value) == false)
{
alert(msg);
obj.focus();
obj.select();
return false;
}
return true;
}