HardwareVertexBuffer problems

Hello everybody,

I had a problem: I created a mesh form HardwareBuffer, Load it, then created an entity... This worked fine. However, if I modified some of the HardwareVertexBuffer, (I wanted to modify the mesh.) But in fact, nothing happened. (I already used this way in OGRE with C++ code, and that can work well).
Have I forgot some important things?? Or there's other way differ from OGRE in MOGRE?? Can SB help me???

It seems to work now:
I devided the VertexBuffer with Position/Normal/Coordinate into three different VertexBuffer(one PositionBuffer, one NormalBuffer, one CoordinateBuffer), and changed each one. And every VertexBuffer can change dynamic. ^_^