'clist for Grid' How can modify?

Attached File is using clist for grid

So, I want to add button

like ‘Clear’ - Clear all checked item

How can modify?

Please, try to add the following code-line in the dhtmlxgrid_excell_clist.js in the nexr line after

<input type=‘button’ value=’"+(this.grid.applyButtonText||“Apply”)…
text+="<div><input type='button' value='Clear checked' style='width:100px; font-size:8pt;' onclick='for (var i=0; i<this.parentNode.parentNode.childNodes.length-2; i++){document.getElementById(\"dhx_clist_\"+i).checked=0}'/></div>"