<script language="JavaScript">
//ให้รับเฉพาะตัวเลข
function checknumber() {
key=event.keyCode
if (key<48 || key>57) event.returnValue = false;
}
//คำนวณเมื่อ KeyUp
function calcfunc() {
var val1 = parseFloat(document.calc.source.value);
var val2 = parseFloat(document.calc.dest.value);
var val3 = parseFloat(document.calc.cre.value)
var val4 = parseFloat(document.calc.cre2.value)