Javascript calculation after values entered.
I currently have the following java script in a adobe pdf to perform calculations. One of the problems I am running into is the form is performing the calculations live. I do not want the calculations to be performed till values are entered. So currently the 3 text boxes are "Neck1", "Neck2" and "Neck3". Once values are entered into these boxes I would like to perform the average calculation. Any help would be appreciated. I am not experience with JavaScript so please be very detailed with answers.
// Custom calculation script (function () {
// Get the field values, as numbers
var v1 = +getField("Neck1").value;
var v2 = +getField("Neck2").value;
var v3 = +getField ("Neck3").value;
var nTotal = (v1 + v2 + v3)
var nAverage = (nTotal / 3)
var nRounded = Math.round(nAverage / .5)*.5;
event.value = nRounded; })();
