I want to create an Excel application level control for Excel 2003,
which gives the user navigator style functionality (i.e. allows them
to view and manage workbooks and worksheets, view comments, named
cells, etc).

I have downloaded a couple of third party "addin" components, as
examples. They "appear" to approach this in one of two ways:

- a form which appears in a custom task pane. I'm assuming this is a
managed .NET COM dll. However, all the documentation I can find says
that it is only possible to create a custom task pane for office
2007. If that is the case, how has this been achieved for Excel
2003?

- a form embedded within a commandbar, and docked to the right of the
screen. Again, I cannot work out how this has been achieved. How do
you specify a windows form as a commandbar control?

Any ideas?