function down_payment(which)
{
    var mortgage = document.CalculatorForm;
    var percentvalue, down, loanamm;

    /* preprocess salesprice */
    loanamm = mortgage.salesprice.value;
    while ((pos=loanamm.indexOf(",")) >= 0)
    {
    sub_1 = loanamm.substring(0, pos);
    sub_2 = loanamm.substring(pos+1, loanamm.length);
    loanamm = sub_1 + sub_2;
    }
    /* preprocess downamount */
    down = mortgage.downamount.value;
    while ((pos=down.indexOf(",")) >= 0)
    {
    sub_1 = down.substring(0, pos);
    sub_2 = down.substring(pos+1, down.length);
    down = sub_1 + sub_2;
    }
    if (which == "downamount")
    {
    percentvalue = Math.floor((parseFloat(down)/parseFloat(loanamm)*100.0)*100) / 100;
    mortgage.percent.value = percentvalue;
    }
    if (which == "percent")
    {
    down = parseInt(parseFloat(loanamm) * parseFloat(mortgage.percent.value) / 100.0);
    mortgage.downamount.value = down;
    }

    /* put comma in dollar values */
    mortgage.salesprice.value = calc_commas(mortgage.salesprice.value);
    mortgage.downamount.value = calc_commas(mortgage.downamount.value);
}

function compu_calc()
{
    var mortgage = document.CalculatorForm;
    var annualRate, monthRate, months, principle, payment, tax, checkprc;
    var loanamm, down, ctax, cloan, pos, sub_1, sub_2;
        
    /* validate certain values */
    
    if (parseInt(mortgage.salesprice.value) <= 0)
    {
    if (parseInt(mortgage.salesprice.defaultValue) > 0)
    {
        mortgage.salesprice.value = mortgage.salesprice.defaultValue;
    }
    else
    {
        mortgage.salesprice.value = "219000";
    }
    }
    if (parseInt(mortgage.downamount.value) < 0)
    {
    if (parseInt(mortgage.downamount.defaultValue) >= 0)
    {
        mortgage.downamount.value = mortgage.downamount.defaultValue;
        mortgage.percent.value = mortgage.percent.defaultValue;
    }
    else
    {
        mortgage.downamount.value = parseInt(parseFloat(mortgage.salesprice.value) * 20.0 / 100.0);
        mortgage.percent.value = "10.0";
    }
    }
    if (parseInt(mortgage.percent.value) < 0)
    {
    if (parseInt(mortgage.percent.defaultValue) >= 0)
    {
        mortgage.downamount.value = mortgage.downamount.defaultValue;
        mortgage.percent.value = mortgage.percent.defaultValue;
    }
    else
    {
        mortgage.downamount.value = parseInt(parseFloat(mortgage.salesprice.value) * 20.0 / 100.0);
        mortgage.percent.value = "20.0";
    }
    }
    checkprc = parseFloat(mortgage.percent.value)
       
    if (parseFloat(mortgage.anintrate.value) < 0.0)
    {
    if (parseFloat(mortgage.anintrate.defaultValue) > 0.0)
    {
        mortgage.anintrate.value = mortgage.anintrate.defaultValue;
    }
    else
    {
        mortgage.anintrate.value = "7.0";
    }
    }
    if (parseInt(mortgage.numberofyears.value) <= 0)
    {
    if (parseInt(mortgage.numberofyears.defaultValue) > 0)
    {
        mortgage.numberofyears.value = mortgage.numberofyears.defaultValue;
    }
    else
    {
        mortgage.numberofyears.value = "30";
    }
    }
    /* preprocess salesprice */
    loanamm = mortgage.salesprice.value;
    while ((pos=loanamm.indexOf(",")) >= 0)
    {
    sub_1 = loanamm.substring(0, pos);
    sub_2 = loanamm.substring(pos+1, loanamm.length);
    loanamm = sub_1 + sub_2;
    }
    /* preprocess downamount */
    down = mortgage.downamount.value;
    while ((pos=down.indexOf(",")) >= 0)
    {
    sub_1 = down.substring(0, pos);
    sub_2 = down.substring(pos+1, down.length);
    down = sub_1 + sub_2;
    }
    /* the real computation */
    annualRate = parseFloat(mortgage.anintrate.value) / 100;
    monthRate = annualRate / 12.0;
    months = parseInt(mortgage.numberofyears.value) * 12;
    principle = parseInt(loanamm) - parseInt(down);
    payment = Math.floor(((principle*monthRate)/(1-Math.pow((1+monthRate),(-1*months)))*100)/100)+(0);
	 tax = Math.round((loanamm*0.0125) / 12);
    
    if (checkprc < 20)    
	 {
      
      insurance = Math.round((principle*0.0035) / 12);
    }
    else
    {
      insurance = "None"
    }
    asking = (219000);	

    /* put value up */
    mortgage.loanamm.value = principle;
    mortgage.monthly.value = payment;    
    mortgage.loaninsurance.value = insurance;
    mortgage.propertytax.value = tax;
    
    /* put comma in dollar values */
    mortgage.salesprice.value = calc_commas(mortgage.salesprice.value);
    mortgage.downamount.value = calc_commas(mortgage.downamount.value);
    mortgage.loanamm.value = calc_commas(mortgage.loanamm.value);
    mortgage.monthly.value = calc_commas(mortgage.monthly.value);
    mortgage.propertytax.value = calc_commas(mortgage.propertytax.value); 
    if (checkprc <20) {    
    mortgage.loaninsurance.value = calc_commas(mortgage.loaninsurance.value); }
}

function calc_commas(target)
{
    var newtarget, decimal, pos, sub_1, sub_2, i;

    newtarget = "";
    /* get rid of existing commas */
    while ((pos=target.indexOf(",")) >= 0)
    {
    sub_1 = target.substring(0, pos);
    sub_2 = target.substring(pos+1, target.length);
    target = sub_1 + sub_2;
    }
    /* extract decimals for safe keeping */
    decimal = "";
    if ((pos=target.indexOf(".")) >= 0)
    {
    decimal = target.substring(pos, target.length);
    target = target.substring(0, pos);
    }
    /* here comes the real work */
    for (i = target.length-1; i >= 0; i--)
    {
    if (((target.length-i-1) % 3) == 0)
    {
        if ((target.length-i-1) > 0)
        {
        newtarget = "," + newtarget;
        }
    }
    newtarget = target.substring(i,i+1) + newtarget;
    }
    /* add on any decimals */
    newtarget = newtarget + decimal;

    return newtarget;
}