Modal dialog delays ribbon update

[Edmundo]

I have my C# add-in bring up a modal dialog. Some code in the dialog
updates a button in the ribbon that is used indicate if the user is or
is not connected to a web service. The code calls InvalidateControl.
My problem is that the ribbon doesn't update until you close the modal
dialog. If the dialog isn't modal, the ribbon updates immediately. I
need to have the ribbon update immediately rather than when the user
closes the modal dialog. How do I force Excel to update the ribbon
when you have a modal dialog open?

Ed