function validatenumber(field) 
{
var valid = "0123456789";
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("Please enter numbers only.");
	field.focus();
	field.select();
	}
}