Like in Outlook 2003, we use the "BtnTest.Priority" to set the button
priority. In Outlook 2007, I want to set the priority to False or 0 so that
when the user resizes the inspector, the buttons hides automatically. eg. the
way the "Names" group on "Message" tab of the Inspector collapses to a
one-button drop down when you re-size the inspector to a smaller size.

Is there an attribute that we can set in the ribbon customui xml to achieve
this?