how to update variables outside base of mrvs values

[flsn2]

Hi 

We have a mrvs that calculates taxes.

We also have 3 variables outside of the mrvs that calculates the final numbers with an onsubmit client script.

This is working okay but our client would like to be able to see the final numbers before sending the request.

i've been trying for hours to sort it out but i'm stuck.

Any help would be appreciate

here is the display

Our current onSubmit script

function onSubmit() {
   //Type appropriate comment here, and begin script below
   

   var mrvs = JSON.parse(g_form.getValue('MRVS VARIABLE SET NAME'));

var subtotal = 0;
var totaltax = 0;
var total = 0;

   for (var i = 0; i < mrvs.length; i++){

	subtotal += parseFloat(mrvs[i].line_item_subtotal);
	totaltax += parseFloat(mrvs[i].line_item_total_tax);
	total += parseFloat(mrvs[i].line_item_total);

   }

   g_form.setValue('subtotal', subtotal);
      g_form.setValue('total_tax', totaltax);
	     g_form.setValue('total', total);

return false;
}