Today I struggled for some time to figure out how to control the visibility of custom task pane in Excel 2007. I had done quite a few Word 2007 addin projects but this is the first time I try to do it in Excel.

In Word 2007 with VSTO 3.0 (that comes with VS2008) to hiding the custom task pane I would add this in the Click event code

Me.Application.TaskPanes(Word.WdTaskPanes.wdTaskPaneDocumentActions).Visible = False

But with Excel 2007 it is different. You have use the DisplayDocumentActionTaskPane class

Me.Application.DisplayDocumentActionTaskPane = False

I found the solution in the MSDN article here.

Just FYI, adding a action pane is same for both application using the following method

Me.ActionsPane.Controls.Add(actions)