How to: Create a mesh from a VertexBuffer?

Good Day,

I have made some basic 3d shapes, namely a cube-like object using Vertices and Vertex Buffers.
I present those shapes using the
d3ddev->SetStreamSource(...);
d3ddev->DrawPrimitive(D3DPT_TRIANGLEFAN,...);
functions.

Now i want to "save" these shapes in a mesh, so i can draw them more easily with
mesh.DrawSubset(0).

I tried to create the mesh using:
D3DXCreateMeshFVF(...);
but unfortunately i am doing something wrong, as nothing is displayed with the
mesh.DrawSubset(0) function.
I think i am missing something, especially the direction i have to give to the mesh as how to draw my shapes

Any help on how i can create this mesh from my vertex buffer would be great!

Thanx in advance,
Stakon.