function calculate(theForm) {
		var valid=true;
		var errorMsg;
		var focusObject;
		var avalue = removeCharacters(theForm.avalue.value);
		 if (!validateNum(avalue) || (avalue<0)) { 
		 	errorMsg = "\"Appraisal Value\" is not a valid entry.\nPlease enter positive numbers";
			valid=false;
			focusObject = theForm.avalue;
		 }
		var percentage = removeCharacters(theForm.percentage.value);
		if  (!validateNum(percentage) || (percentage<0) || (percentage>0.9)){  
			errorMsg ="\"Loan-to-value ratio\" is not a valid entry.\nPlease enter positive numbers between 0.1 - 0.9";
			valid=false;	
			focusObject = theForm.percentage;
		}
		var lessmortgage = removeCharacters(theForm.lessmortgage.value);
		if (!validateNum(lessmortgage) || (lessmortgage<0)) {
			errorMsg ="\"Less mortgage debit\" is not a valid entry.\nPlease enter positive numbers";
			valie=false;
			focusOjbect = theForm.lessmortgage;
		}
		if (valid) {
			var tmp1 = (avalue * percentage);
			theForm.maxamount.value = tmp1;
			var tmp2 = tmp1 - lessmortgage;
			theForm.pamount.value=tmp2;
		} else {	
			alert(errorMsg);
			theForm.pamount.focus();
			focusObject.focus();
			focusObject.select();
		}
	}
	
	
	function removeCharacters(str) {
		var tmp = str.replace(/[,| ]/gi,"");
		return tmp;
	}

	function validateNum(num) {
		var validPattern =/(^[+|-]?[\d]*(\.)?[\d]+$)|(^[+|-]?[\d]+(\.)?[\d]*$)/;
		return num.match(validPattern);
	}