Simple question: 1 external wall 2 types of siding.

[twincreeks]

_____________________
|
|
|
|_____ _____________|
|
|
|________|


Hi, I have a simple plan sort of like the ASCII above (I'm having trouble getting it formatted right, but the text should explain) . In the picture above, I show a large room and then a small room which has an interior wall. The large and small rooms share an external wall shown in the diagram as the left wall. I wish to make this external wall use different types of siding, on each side of the interior wall, so that the small room has a different external siding that the large room. How do I accomplish this ?