function checnum(as)
{
	var dd = as.value;
	if(isNaN(dd))
	{
		dd = dd.substring(0,(dd.length-1));
		as.value = dd;
	}		
}
function calculate(form)
{
	var grossIncome = form.grossIncome.value;
	var totalDebtAllowed=grossIncome*.4;
	var ccDebt =form.ccDebt.value;
	var autoLoans =form.cars.value;
	var otherLoans =form.otherLoans.value;
	var totalOtherDebt=Number(ccDebt)+Number(autoLoans)+Number(otherLoans);
	var intRate=form.intRate.value;
	var housingDebtAllowed=totalDebtAllowed-totalOtherDebt;
	var principalInterestDebtAllowed=housingDebtAllowed*.78;
	var valueA=Math.pow(((intRate/1200) + 1),360);
	var mortQualification=Math.floor(principalInterestDebtAllowed * ( 1 - ( 1 / valueA) ) / (intRate / 1200), 1);
	if (isNaN(mortQualification))
		return;
   else {
   // format the output
   mortQualification = mortQualification.toString().replace(/\$|\,/g,'');
	if(isNaN(mortQualification))
		mortQualification = "0";
		sign = (mortQualification == (mortQualification = Math.abs(mortQualification)));
      mortQualification = Math.floor(mortQualification*100+0.50000000001);
      mortQualification = Math.floor(mortQualification/100).toString();
      for (var i = 0; i < Math.floor((mortQualification.length-(1+i))/3); i++)
		mortQualification = mortQualification.substring(0,mortQualification.length-(4*i+3))+','+
		mortQualification.substring(mortQualification.length-(4*i+3));
		form.loanQualifed.value='$'+mortQualification;
   }
}