IGeoprocessor - Sort

Hi,
I desperately try to implement the "Sort" Geoprocessor.
Everything seems to be ok, except of the value "sort_field" where I want to implement a descent sort.

What's the syntax in VB.NET to add the DESCENDING command to the sort field?
"ELEVATION_""DESCENDING" is not working.

Thanks a lot!
Corko

GP2 = New Geoprocessor
Dim Sort As ESRI.ArcGIS.DataManagementTools.Sort
Sort = New ESRI.ArcGIS.DataManagementTools.Sort
Sort.in_dataset = "EHED_OBSP_RAW"
Sort.out_dataset = "EHED_OBSP_RAW_500"
Sort.sort_field = "ELEVATION_"
GP2.Execute(Sort, Nothing)