Is there a way to configure an Excel Workbook so that it displays in
the dashboard?
Widgets are bundles of HTML, CSS, and JavaScript, and you can develop
plugins, so I'd think it would be possible to so so, though I've never
done so.
http://developer.apple.com/documentation/AppleApplications/Conceptual/Das
hboard_Tutorial/Widget_Basics/chapter_3_section_1.html#//apple_ref/doc/ui
d/TP40001340-CH203-TPXREF101
To display, you could save the Worksheet as HTML and add it to your
widget bundle.
If you need to drive XL with the widget, you might be able to develop an
applescript plugin.