I have an add-in created in VS2005SE C# for Excel2003.

In the opened workbook I have to save some hidden informations. For that I
save them to a specific sheet of the workbook. These hidden informations are
saved when the workbook is deactivating and the workbook is in place.

My problem is that even if i place in the sheet my informations, the
informations are not saved. For this I've decided to call Workbook.Save. But
I get an error

System.Runtime.InteropServices.COMException (0x800A03EC): Exception from
HRESULT: 0x800A03EC
at Microsoft.Office.Interop.Excel.WorkbookClass.Save( )

Is there a way to save the workbook even if it is inplace? Or perhaps
another solution to my problem?

The workbook is opened inplace through IOleObject.DoVerb