I am trying to make checkbox1 change font color, background color and
add/remove border lines if possible.

I am really not sure how to write the code for this at all. I would like to
change the font from black to yellow, and the background color in cell A3,
B3, C3 (one merged cell) from white to yellow. I would also like the black
border line around the cell to change as well, but I am not sure if that is
possible?

Thanks.