Dynamically Configure Image Combo in Treegrid from XML

I can load a combo in a treeGrid excell from xml no problem, as in:

<row id="2a"> <cell class="form_cell">Example 1 Combo</cell> <cell type="combo" mode="image" align="left" xmlcontent="1">B <option value="1">A</option> <option value="2">B</option> <option value="3">C</option> <option value="4">D</option> </cell> </row>

But I cannot seem to dynamically configure the combo through XML to accept images. I notice in the init example here: http://www.dhtmlx.com/docs/products/dhtmlxCombo/samples/01_init/03_object_api_init.html that there are several initialization flags:

mode: "image", name: "combo3", image_path: "../common/flags/", default_image: "flag_green.png", default_image_dis: "flag_gray.png",

How can these be accessed to enable images dynamically from XML?

Should I assume from the lack of support or response that I will have to roll my own?

Unfortunately the combo with images is not available with combo exCell type.