IUNKOWN with ABBYY Finereader DISP_E_UNKNOWNNAME

Hi,
recently I acquired a Trial Version of ABBYY Finereader SDK (COM) and Installed it on our Server at work.
- The Task is to work with this SDK directly in Nav (No building addin a wrapper).
- Many things seem to be functioning well, except for one method "Export"

engine.Export(path,fileType,exportParams);

- "exportParams" is of type IUNKNOWN (in Nav), but actually it's a System.object
- possible object to be passed in "exportParams" are "RTFExportParams", "XMLExportParams".
- The dll has methods to create These objects, see below:

      // steps to create an "engine"
      XMLExportParams := engine.CreateXMLExportParams();
            //...
      engine.Export(path,fileType,XMLExportParams);

- Unfortunately, "Export" throws an exception (HRESULT: 0x80020006 (DISP_E_UNKNOWNNAME)) at runtime (It does compile successfully), due to the exportParams.
- I have already tried defining a VARIANT variable that i assign to the "XMLExportParams". .

    variantVariable :=XMLExportParams 

That did not solve it.
I understand IUnknown is the base type for COM Objects. So, Such a param should be able to accept any object type, but here it seem not to be the case.
Any Suggestions are Welcome.
Thanks