function resetRoll() {
	document.forms[0].elements[1]="";
	}

function  calcRoll() {
    if(validNumber(document.getElementById('length'), 'length') == true) {    
        if(validNumber(document.getElementById('width'), 'width') == true) {  
            var length = (document.getElementById('length').value)
	        var width = (document.getElementById('width').value)
           	
	        var prodRect = (length  *   width / 8.5).toFixed(2)
			
	        document.getElementById('ansRoll').value = prodRect
	        }
	    }
	}



function validNumber(varInput, fieldName) {

    if (varInput.value == null) {
            alert('Please enter a number for the ' + fieldName + ' field.');
            varInput.focus();
            return false;
        }

	if (IsNumeric(varInput.value) == false) { 
		    alert('Please enter only numbers and decimal points for the ' + fieldName  + '.');
		    varInput.focus(); 
		    return false;
		} 

return true;
}



function IsNumeric(strString) {
       var strValidChars = "0123456789.";
       var strChar;
       var blnResult = true;

        if (strString.length == 0) return false;

       //  test strString consists of valid characters listed above
       for (i = 0; i < strString.length && blnResult == true; i++)
          {
          strChar = strString.charAt(i);
          if (strValidChars.indexOf(strChar) == -1)
             {
             blnResult = false;
             }
          }
                 
       return blnResult;
   }