Once again, it's an issue with IE, in this case not supporting the previousElementSibling property. Change it to previousSibling and it works fine. I've only tried it in IE8, dunno about 7 or 6.

I'm only worried about 8, and all seems to work fine now - thanks.

Using the function supplied earlier, some of the numbers coming in are in the thousands, and have helpfully been formatted to include comma separators.
I found a snippet of javascript that removes commas, but it doesn't seem to work. Anyone care to have a go at explaining what I've done wrong this time? ;-)

<script type="text/javascript">
//Get the values from the table when checkboxes are checked
var getCheckboxes = function () {
    var i, elements = document.getElementsByTagName("input"),
        max = elements.length,
        result = [];
 
    for (i = 0; i < max; i += 1) {
        if (elements[i].type === "checkbox") {
            result.push(elements[i]);
        }
    }
    return result;
    DeleteComma(result);
};

<script type="text/javascript">
function DeleteComma(num) {
var temp1 = 0;
var xarray = num.split(",");
if ( xarray[2] != null ) {
   temp1 = xarray[0]+xarray[1]
+xarray[2]; return temp1 } 
else if ( xarray[1] != null ) {
          temp1 = xarray[0]
+xarray[1]; return temp1}
       else
{temp1 = xarray[0]; return temp1 }         
}
</script>

Um, that seems like a vastly over-complex function just for removing commas from a string.

var deleteCommas = function (num) {
    return (num + "").replace(/,/g, "");
};

But aside from that, you're calling DeleteComma() on the result of a function that generates a list of checkboxes. There are no commas to delete from such a list. Moreover, you'e calling it after the function has returned, so it never actually gets exectuted.

edit:
Looking over the code, the bit you need to change is this loop:

for (i = 0; i < max; i += 1) {
    if (checkBoxes[i].checked) {
        // Get values directly from table cells.
        total += +checkBoxes[i].parentElement.
            previousElementSibling.innerHTML;
        totalWholesale += +checkBoxes[i].parentElement.
            previousElementSibling.previousElementSibling.innerHTML;
    }
}

Change it to this:

var element, deleteCommas;
 
deleteCommas = function (num) {
    return (num + "").replace(/,/g, "");
}; 
 
for (i = 0; i < max; i += 1) {
    if (checkBoxes[i].checked) {
        element = checkBoxes[i].parentElement.previousSibling;
        total += +deleteCommas(element.innerHTML);
 
        element = element.previousSibling;
        totalWholesale += +deleteCommas(element.innerHTML);
    }
}

edit again:
Actually to make it even more resilient, you could change deleteCommas() to:

stripNonNumeric = function (num) {
    return (num + "").replace(/[^0-9.]/g, "");
};

That way it would remove things like currency symbols or extra spaces or whatnot - anything that isn't a digit or a .

Cheers - much appreciated once again!