Transfer VNC/Screen Sharing to other mac?

[cmillermo]

Ok so heres my problem, my cousin recently moved to france. Before he left he let me register as a user on his computer so that I can screen share with him without asking while hes on a different network because he often has computer problems he needs help with. But I set this up on my Imac (with snow leopard). Most of the times that he calls me for help im away from my Imac with my macbook pro (leopard) but I can't connect to his computer from my macbook. So my question is: is there any way for me to screen share with him from my macbook, without bringing him to my network or using Ichat? Thanks a bunch