do --The battle manager registers its own unit selection handler for some cases, --but it clears it out if there's not a registered callback. The following --do-block tells the battle manager to keep its selection handler: do local dummy_callback = { unit = nil, callback = function() --[[do nothing]] end; }; if #bm.unit_selection_callback_list == 0 then bm:register_unit_selection_handler("battle_manager_unit_selection_handler"); end; table.insert(bm.unit_selection_callback_list, dummy_callback); end; --Now that we've made sure the battle manager's selection handler will work, --we override the old, global function that it uses so that we can --piggyback on its functionality --This way we can use the selection handler that already exists --without needing to add our own one that will interfere with the existing one. local original_handler = battle_manager_unit_selection_handler; battle_manager_unit_selection_handler = function(unit, is_selected) original_handler(unit, is_selected); --This is where you can call your own function, like this: ClickAndFight_UnitSelectionHandler(unit, is_selected); end; end;