Check Boxes and Javascripts

Question

I have a form where there is a table, and inside the table is a row for a Check box for “Sub to Sub”, a row for Work performed by Sub-Contractor Description, a row for Original $$ Amount, and a row for Final $$ Amount Paid.  The Original Amount and Final Amount Paid totals up at the bottom of the page. 
The user would like to have it set that if the Sub-Contractor selects a check box under “Sub to Sub” row, the dollar amount that is entered for the Original Amount and Final Amount Paid for that row does not add into the Total amounts at the bottom of the page. 
Is it possible to write a Javascript for this and if so, what would it be?

Answer 1

Okay.  I put it in the first calculated script which is the total for Original Amount (OA1).  The checkboxes are named Checkbox1.1, Checkbox1.2, etc. But it's not calculating at all.  Any suggestions?
(function () {
    var f1 = this.getField("OA1");                            
    var a1 = f1.getArray();
    // Get the "Sub to Sub" check boxes
    var a2 = getField("CheckBox1").getArray();
    var sum = 0;
    for (i = 0; i < a1.length; i++) {
        // Only add the value if the check box is not selected
        if (a2[i].value === "Off") {
            sum += +a1[i].value;
    if (sum != 0) {
        event.value = sum;
    } else {
        event.value = ""
Thanks
Connie