Automatisk beregning?

Jo...
<form>
  <script type="text/javascript">

function beregn( frmObj ) {
var t1 = parseInt( "0"+frmObj.Felt1.value, 10 );
var t2 = parseInt( "0"+frmObj.Felt2.value, 10 );
frmObj.samlet.value = (t1 +t2);
}; //end beregn( HTML Form objekt )

</script>
<p><input type="text" name="Felt1" value
  onblur="beregn(this.form);" size="20"><input type="text" name="Felt2" value
  onblur="beregn(this.form);" size="20"><input type="text" name="samlet" value
  onfocus="this.blur();" size="20"></p>
</form>