First let me say I'm pretty new to windows programming and that I am using MFC in this application because that is what the previous programmers built it with. What I am trying to do is create a mouse selection over a specific square area in the application where a 2D image is held. Right now I can check what area the user selects and calculate it from where the cursor is when ON_WM_LBUTTONDOWN is sent and where it is when ON_WM_LBUTTONUP is sent. However, I'm not sure how to make an actual drag selection, and one that is transparent inside the selection. I took a look at this thread but it doesn't seem like there was ever a consensus there. Fordy's post makes the most sense to me, but PtInRect documentation makes me think that the cursor on the edge of the selection (since it would always be the end point) wouldn't be in the rect. The other thing is that I have never used any sort of paint functions and am not quite sure how they work. Thank you for at least reading this, if you can offer any help I thank you for it.