DlangUI MouseEvent mouse delta

[stunaep via Digitalmars-d-learn]

I am trying to know how much the mouse moves when clicking down 
on a certain widget, but I can't figure out how. I noticed only a 
mouse wheel delta property and nothing for the mouse pointer x,y 
deltas since the click. I am looking to do something such as

if(e.lbutton().isDown() && !e.rbutton().isDown()) {
    pitch -= e.dy();
}