Note that the IRange.AutoFilter() method is overloaded, which provides the extra parameters you'd need to do this. Example:
fundfilter.AutoFilter(2, "Hedge funds", AutoFilterOperator.Or, null, true);
See the following Silverlight sample for more examples of using this auto filter API: http://www.spreadsheetgear.com/support/samples/silverlight.aspx?InitSample=SilverlightSamples.Range.AutoFilterSample
The SpreadsheetGear for .NET and SpreadsheetGear for Silverlight products share much of the same underlying core APIs, so this example is relevant for either products.