Can I use user controls in my own toolbar (Office 2003)?

Now I need to develop my own add-in for Office 2003 (Word and Excel). The
best wishes from our customer is to place our toolbar at the right - like
Getting started toolbar - with our own user control on it...
Other solution will be placing common windows forms controls like checkbox,
combobox and other to this new toolbar to form necessary data...
Can I do this with VSTO and Visual Studio 2005? Now I can only place buttons
to my own toolbar :(

thank you for your help.
Olga


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