Johannes,
Yes, you can do that in at least Word 2003. You can do that by supporting
the SmartDoc Interface in a Win32 COM component or a .Net assembly (we have
created solution with both VB and C#). You really don't create your own task
pane but you populate it with what you want, like text controls, buttons,
bitmaps, text fragments, ActiveX controls and so on. You have also full
control over what should be displayed in the task pane depending on where in
document the insertion point is (by triggering different XML tags in the
document).
We demonstrated that in Microsoft's booth at a computer fair last week. We
got very possitive responce and a lot of interest in what you can do with
SmartDoc solutions and people really liked what they saw.
Regards,
Lars-Eric