Combo, dhxcombolist_dhx_skyblue and z-index

I have a dhtmlxcombo create by a dhtmlxform in a scheduler lightbox…
All work fine but the list of options is on z-index of 105, so it’s behind the lightbox with the zindex of 10001 …

How can I change the z-index of this list witch is made directly by the code with dhxcombolist_dhx_skyblue class but also with style in the element and with the mention of z-index directly in it ?

try decreasing the z-index of the lightbox popup,

.dhx_cal_light{ z-index:100 !important; }