Add the onLBDblClick event handler to your listbox.
class YourDlg
{
... blah blah blah;
... blah blah blah;
class C_YOUR_LIST: RscListBox
{
... blah blah blah;
... blah blah blah;
onLBDblClick = "[""onLBDblClick"", _this] call YourDlgEventHandlerFunction";
};
};