//volume calculator code for gorham sand and gravel tool.

function calcConc(form)
	{
     	var concAmt = 0;
       	for (var i = 1; i <= 3; i++) {
          	var parsecheck = "" + parseFloat(form.elements[i].value);
          	if (parseFloat(form.elements[i].value) < 0 ||
          			parseFloat(form.elements[i].value) == 0 ||
                  	parsecheck == "NaN") {
                   	window.alert("Please enter a positive number in each of the " +
                                   "three input fields.");
                 	return false;
           		}
          	}
         	if (form.elements[4].checked == true)
         		concAmt = form.elements[1].value * form.elements[2].value *
              		(form.elements[3].value / 12.0) / 27;
         	else
         		concAmt = form.elements[1].value * form.elements[2].value *
                  	form.elements[3].value / 27;
                form.elements[8].value = formatvalue(concAmt,7);
                return true;
            }

           function formatvalue(input, rsize)
            {
               var invalid = "**************************";
               var nines = "999999999999999999999999";
               var strin = "" + input;
               var fltin = parseFloat(strin);
               if (strin.indexOf("e") != -1 ||
                   fltin > parseFloat(nines.substring(0,rsize)+".4"))
                  return invalid.substring(0, rsize);
               if (strin.length <= rsize) return strin;
               var rounded = "" + (fltin +
                  (fltin - parseFloat(strin.substring(0, rsize))));
               return rounded.substring(0, rsize);
            }

            function clearform(form,count,lastElement)
            {
                for (var i = 1; i <= count; i++) form.elements[i].value = "";
                form.elements[8].value = "";
            }