Combobox Find Itmem using uniqueidentifier

Question

I have a combobox databound to a table, Regions. The DataTextField is set to region name and the DataValueField is set to RegionID which is a unique identifier GUID.
Region.SelectedIndex = Region.FindItemIndexByText(rowView["RegionKey"].ToString());
Region.SelectedIndex = Region.FindItemIndexByValue(rowView["RegionKey"].ToString());
Neither of the above statements work with the GUID. How do you FindItemIndex with GUID`s
Regards, Lee