Combobox with two different images for selection

I want use two different image for selection (program code: “z.src = (window.dhx_globalImgPath?dhx_globalImgPath:”")+‘combo_select.gif’;") according combo readonly property

What is the easiest way to do it?

You can modify readonly method of dhtmlxCombo and add logic, which change image to different one
    combo.DOMelem_button.src=‘some_other_select.gif’;