OpenCV passing values by reference or pointer to callback functions

I'm trying to avoid using global variables in an openCV project (I'll have my supervisor no doubt teach me as to why they are bad rah rah rah :) - but at the moment they seem to be the only way I can get information out of mouse and trackbar callback functions.

Using the mouse example - at the moment I have as globals:

vector<Point2d> vectorOfPoints;
int clickCount = 0;

At the moment I have this line in main:

setMouseCallback("test",onMouse, NULL);  

Then above main:

void onMouse(int event, int x, int y, int f, void* ){           
    if(event == CV_EVENT_LBUTTONDOWN){  
        vectorOfPoints.push_back(Point(x,y));
        clickCount++;
    }
}

It is working, but what is the syntax to get read/write access to both vectorOfPoints and clickCount inside the callback function without using globals?

I have found this question online a few times but the answers are unclear to me or wont work. There are hints within comments as how to do it, but I am so far unable to interpret the jargon correctly.

I was hoping for something as simple as the syntax I use to pass variables as references to methods ...

void referenceExampleMethod(vector<Point2d>& referenceExample){
    //do something with referenceExample...
} 

...less convoluted the better

I'm scared to ask (jargon overload!) but maybe it's 100% relevant - what is void* ??

Any help appreciated