Pass 3rd value from DD Array into eCart?

I'm using DD to filter product variables for my eCart.

The first drop down allows selection of product model/size.
This populates my eCart description column.

The second drop down dynamically shows the colors available for the model selected.
The label goes into my eCart color column. The value contains the price, which goes into the eCart price field.

I need to populate the size column in my eCart from the same array as the color table.

Here's my DD array:
echo "WAJA[".$n."][".$m."] = new Array();\n";
echo "WAJA[".$n."][".$m."][0] = "."'".WA_DD_Replace($row_sizesRS["colorID"])."'".";\n";
echo "WAJA[".$n."][".$m."][1] = "."'".WA_DD_Replace($row_sizesRS["color_name"])."'".";\n";
echo "WAJA[".$n."][".$m."][2] = "."'".WA_DD_Replace($row_sizesRS["colorprice"])."'".";\n";
echo "WAJA[".$n."][".$m."][3] = "."'".WA_DD_Replace($row_sizesRS["colorsize"])."'".";\n";

I'm trying to populate "colorsize" into a hidden field onChange that will bind to my eCart size column.

I've tried several JavaScript techniques but can't get it to work.

Anyone have any ideas?

Thanks