I'm not quite sure what you are saying, but its almost certainly possible. You can have the same mask doing several jobs in Vue. If you create a mask in the shape of the graffiti, you can use this to drive 'mixed materials'. You can then put the graffiti texture and the wall texture on the same object and they will look ok. You can make the Graffiti material a mixed material itself, using the 'wall' bumps to texture it. I have recently used this technique to add 'real' water to one of my 'real landscape' models. (www.derby-vi-service.demon.co.uk/pictures.htm and follow the link to Real Landscapes) Sorry if this is not clear, but I'm not in front of Vue at the moment. Almost antything can be achieved with a bit of ingenuity and a knowledge of what masks can do in Vue. Get in touch if you want me to make the material for you, so you can see how it is done. I could make a simple example and send you the material file.