First, I'd create a macro to toggle between showing and not showing comments:
Code:
Sub ToggleComment()
'Macro created by 4XL Solutions on 9/19/06
If Application.DisplayCommentIndicator = xlCommentAndIndicator Then
Application.DisplayCommentIndicator = xlCommentIndicatorOnly
Else
Application.DisplayCommentIndicator = xlCommentAndIndicator
End If
End Sub
Then, I would create a button (View-> Toolbars-> Forms, then select and draw a button). When prompted, point your button to run the ToggleComment macro.