VB: Matrices: Object manipulation

Hi, I'm having some trouble working out how to manipulate a single mesh when I have multiple meshes in my world.

At the moment, my mesh creation code is:
        Set objMesh(Index).Mesh = myDX.D3DX.LoadMeshFromX(App.Path & "\resources\models\" & strModel & ".x", D3DXMESH_MANAGED, myDX.D3DDevice, Nothing, mtrlBuffer, objMesh(Index).nMaterials)

My matrix manipulation code is:
        D3DXMatrixTranslation matTranslation, 0, 0, 0
        D3DXMatrixRotationYawPitchRoll matRotation, RotX / 5000, RotY / 5000, RotZ / 5000
        D3DXMatrixScaling matScaling, 1, 1, 1
        D3DXMatrixMultiply matTransform, matRotation, matTranslation
        D3DXMatrixMultiply matTransform, matTransform, matScaling
        D3DDevice.MultiplyTransform D3DTS_WORLD, matTransform

I understand the general theory behind it, however I have no idea how to rotate a single object. Whenever I use code like this it just rotates everything.

Thanks for any assistance,
Knossos.