<!--
function showroi() {
 if (
(document.calc.visitors.value == null || document.calc.visitors.value.length == 0) ||
(document.calc.leads.value == null || document.calc.leads.value.length == 0) ||
(document.calc.salesconv.value == null || document.calc.salesconv.value.length == 0) ||
(document.calc.websalevalue.value == null || document.calc.websalevalue.value.length == 0) ||
(document.calc.webspend.value == null || document.calc.webspend.value.length == 0)
)
 { document.calc.roi.value = "Incomplete data";
 }
 else
 {
var numsales = (document.calc.salesconv.value / 100) * (document.calc.leads.value); 
var totalsales = document.calc.websalevalue.value * numsales;
// roi
document.calc.roi.value = (((totalsales - document.calc.webspend.value) / document.calc.webspend.value) * 100).toFixed(0) + '%';
// roi explained
document.calc.roiexplained.value = '$' + ((totalsales - document.calc.webspend.value) / document.calc.webspend.value).toFixed(2);
 }
}
// -->