Implementing your own Undo context using AddFilter

Hi,
I have an editor with IOleCommandTarget implement and I have setup a filter using AddCommandFilter,

I on IOleCommandTarget I receive call for Microsoft.VisualStudio.VSConstants.VSStd97CmdID Undo,Redo, MultiLevelUndo, MultiLevelUndoList, MultiLevelRedoList and MultiLevelRedo,

But I cannot find any documentation about what is coming in pvaIn, pVaout parameters or what structures them are, also I want to be able to fill the lists on MultiLevelUndoList and MultiLevelRedoList so VS can show these lists on undo/redo combos

Can you share some code or point me to some documentation that explain how to correct handle and implement these scenarios?

Thank you very much in advance

Jesus salas