geometry shaders?

hello, is it possible to create geometry shaders with CG in shaderlab?

if yes, how?

thanks!

The forum already answers your question:

http://forum.unity3d.com/threads/80069-Is-Geometry-Shader-supported-in-Unity3D

The answer is NO

You can use CG code inside a Pass block. Take a look at the reference: Writing vertex and fragment shaders