How to get an IWin32Window for Excel embedded in Word/PowerPoint
 

I have an add-in written in C# and i'm trying to show a windows form so that
will not get hidden.

I know that the Application has a Handle that I can use to show the form,
but if I try this with excel embedded my form still gets hidden.

Is there a way to get the Handle of the object that contains the excel?

Also I have tried to get the Container from the Workbook but an exception is
thrown:
COMException (0x800A03EC): Exception from HRESULT: 0x800A03EC