<script>
var ok = ” This chip will work”;
var nook = “This chip will not work”;
function check_input()
{
var entry = document.forms.f.textfield.value;
var length = entry.length
document.clear();
res = isNaN(entry) ? “please enter only numbers”: “Press OK to continue”;
alert(res);

if(length == 15) document.write(ok);
else
document.write(nook);
}
</script>