Solucion:
Código Javascript
:
Ver original<!--
function Suma(isChecked, myValue)
{
tot = parseFloat(document.form1.total.value);
myValue = parseFloat(myValue);
if (isChecked) document.form1.total.value = tot + myValue;
else document.form1.total.value = (tot - myValue).toFixed(2);
}
//-->