Interface And Graphics :: Best Way To Make A 'tile Selector' Box?

So now I will try to make something more complex, still playing around with this graphics thing.I want a picturebox to display a tileset (a bunch of 32x32 tiles normally used for creating game levels etc), the picturebox is inside a container (which has autoscroll ON). The picturebox is larger than the container, so the container will make scrollbars automatically.Now, I need to be able to choose a tile or multiple tiles (if I click & drag the mouse)Basically I want to draw a 32x32 "red" box over each selected tile (so the user knows what tiles are selected).So first of all, I need to know when the mouse clicks the picture. Good. It works.Now, I need to know which 32x32 tile was clicked. Well, I think I can calculate that just fine.BUT, what if the user drags the mouse while clicking on a tile? I want to support multiple tiles selected, but I am clueless about tracking what tiles were chosen.If we solve that problem, I would have another curiosity: You know the "red boxes" that tell you which tiles are selected? What would happen if I dragged the scroll bar? I need the redboxes to move along with the picture, and hide if they go to an invisible area.