Increase array value on every button click?

I am creating a calculator in C #. I'm not sure if the best way is to increase the number in the array every time the button is pressed. Here is one of my current button event handler methods:

    //Assign button '2' to 2 with array address of 1
    private void num2_Click(object sender, EventArgs e)
    {
        numbers[1] = 2;
        lblUpdate(1);
    }

      

        
        
        
      

    

I'd like so much that every time this button is pressed, the numbers [1] are incremented by 2. Right now, it just sets to 2 no matter how many times the button is pressed.

Many thanks!