Create another menu which mirrors child elements

I am currently using superfish for a horizontal main menu on my site with drop downs. What I want to do is to create an additional vertical menu which will go down the left hand side of the page on pages which are on the drop down menus. Hence say I have top level menu items A, B,C,D,E and B and D have drop down items B1,B2,B3 and D1,D2,D3 etc I want to have a vertical menu appear when I am on either the B page or any of the B1, B2 etc pages so that there is an alternative menu to help with navigation. However I cant see a way to mirror the elements from the main superfish menu to another one - Is there any way of achieving this?

Thanks