Tabindex for dhtmlx combo

I am setting the tabindex property of all of the controls on my web form, and I need to be able to do this with the dhtmlx combo boxes on this form.

Is this possible? If so, how?

If combo was created from selectbox it will inherit tabindex from original select.
If combo was created by the script you can use 5th parameter of constructor

    var z=new dhtmlXCombo(parent_id, name, width, “”, tab_index);