"Drag" selection box...how to?

[Bishop, Michael W. CONTR J9C880]

Hello,      I’ve worked with listeners to drag and drop elements around a JSVGCanvas.  This method works primarily by registering which elements receive the mouse up/down events.  What I want to do is implement a selection “box” where you drag a box around a number of elements and it will select all the elements that fall within that box.  I need some way to translate screen coordinates to document coordinates which is a known problem.  What I don’t know how to do is ask the document “Which elements fall inside this box?”   Michael Bishop