How can a plugin know the host version ?

Hello,

My format plugin needs to know which host version is calling it (CS2, CS3, ...) to adapt automatically (ex: CS2 does not support creating images with multi-layers). How can I get the host version from the plugin ?

Up to now, I have been using  HostSupports32BitCoordinates to distinguish between before and after CS1 but I need more precision (actually, I need to distinguish hosts between before and after CS3).

Thank you!

Gilbert