As far as I can tell there's no way to do that. You're probably better off creating your own tasks if you want to do that.

We had a look and it is possible to do this. The code below should get you started:

KRD_fnc_taskSucceeded = {
    params ["_logic", "_operation", "_args"];

    switch (_operation) do {
        case "handleEvent": {
            // do your reward stuff here
            // task data is in _args
        };
    };
};

private _listener = [nil, "create"] call ALIVE_fnc_baseClass;
_listener setVariable ["class", KRD_fnc_taskSucceeded];

private _listenerID = [ALIVE_eventLog, "addListener", [_listener, ["TASK_SUCCEEDED"]]] call ALIVE_fnc_eventLog;