using the backbuffer as a texture?

Hi, I''m making a game engine on VC++ 6.0 using DirectX 8, I''m drawing everything with DX sprites (it''s a 2d engine) and now I''d like to add filters that allow you to play at double resolution and the like, so is it possible to either a) set the destination of the sprites to a surface other than the backbuffer, so I could draw everything into a texture and then just put that on the backbuffer at double size b) copy a section of the backbuffer to a texture, then redraw at larger size.