Use the MouseDown. MouseMove and MouseUp in conjunction with each other. Set form properties to store the locations ie for each time the user does mousedown with the Ctrl key pressed you log the XY coordinates in an array....

I'm trying to draw a marquee on the map to allow selection of multiple pushpins my mousedown event records the xy start coordinates, my mouseup event records the xy end coordinates - if they are not the same the user has dragged across the map. Convert xy coords to location and calculate width, height of shape and add the shape - well it's a good plan except my shape isn't appearing!

Anyway hope that helps...