Why doesn't work on first keypress

[Ghosty]

I have this code i got it from this forum and modified it a bit but i'm having a problem:
when i type the first number in the textbox id="qty1" it doesn't modify the other textbox.
for example type 0.68 to see what i mean.
it gives 4.80 when it should give 5.44
meaning it does 8x0.6

thnx,

 
<?php
echo '<html xmlns="http://www.w3.org/1999/xhtml">
 
<head>
<script type="text/javascript">
 
function calct1(unId, quId, stId) {
    var un1=document.getElementById(unId).value;
    var qn1=document.getElementById(quId).value;
    var x1=parseFloat(un1);
    var y1=parseFloat(qn1);
    var z1=(x1*y1);
    var sb1=z1.toFixed(2);
    document.getElementById(stId).value=sb1;
}
 
</script>
</head>
<body>';
echo'    <input type="text" id="unit1" size="6" maxlength="6" value="8.00" readonly="readonly">';
?>
    <input type="text" id="qty1" size="6" maxlength="6" value="0" onkeypress="calct1('unit1', 'qty1', 'sub1')">

    <input type="submit" value="Calc" onClick="">
<?php
echo'
    <input type="text" id="sub1" size="6" maxlength="6" value="0.00">
    <br/><br/>
    <input type="text" id="unit2" size="6" maxlength="6" value="8.00" readonly="readonly">
    <input type="text" id="qty2" size="6" maxlength="6" value=0 onClick="(this.value="")">
    <input type="submit" value="Calc" onClick="calct1("unit2", "qty2", "sub2")">
    <input type="text" id="sub2" size="6" maxlength="6" value="0.00">
</body>
</html>';

[Logic Ali]

Use the onkeyup event instead.

[Ghosty]

Tjnx for the help. :)