<!--
function calculate(obj, inform) {
    with (inform) {
        if ( U2.options[U2.selectedIndex].value != 0 && isnum(V1.value) ) {
            V2.value=V1.value * U1.options[U1.selectedIndex].value
                    /U2.options[U2.selectedIndex].value;
        }
    }
}
function isnum(num) {
    if ( num == "" ) {
        return false;
    }
    for (var i=0; i < num.length; i++) {
       var ch= num.substring (i, i+1)
       if ((ch < "0" || ch > "9" ) && ch != ".") {
            return false;
       }
    }
    return true;
}
 
// -->