Calculations with Rounded Numbers

Question

I've created a form in Adobe X that has a few calculated fields.  For ease of conversation, we'll call them Field A, Field B and Field C (see below).  I need Fields A and B to be rounded to the nearest whole number so that Field C is also a whole number.  I've tried formatting Fields A and B to show no decimals but the calculaton is still being performed on the non-rounded numbers.  Can anyone help with this?  Thanks.
Field A - Field B = Field C

Answer 1

George I must be missing something.  I added the math.round functions as shown in your example but now it doesn't calculate at all.  Can you look at the coding shown below and let me know where I went wrong?  Thanks.
Updated Coding:
(function(){
var totalMiles = math.round(+this.getField("Total Miles DrivenRow1").value);
var homeMiles = math.round(+this.getField("Home Base MilesRow1").value);
var diff = totalMiles - homeMiles;
if (diff<0) diff = 0;
event.value = diff;})();
Original Coding:
var totalMiles = +this.getField("Total Miles DrivenRow1").value;
var homeMiles = +this.getField("Home Base MilesRow1").value;
var diff = totalMiles - homeMiles;
if (diff<0) diff = 0;
event.value = diff;