Please Help How to Extract Pages from File

Here are my code take from the sample:
 
           string fileName = @"..\..\Test Files\sample1.pdf";
         
            string OutputFile3 = @"..\..\Test Files\sample1_extracted3.pdf";
            string OutputFile4 = @"..\..\Test Files\sample1_extracted4.pdf";
            // Check to see if the library has been successfully unlocked
            if (qp.Unlocked() == 1)
            {               
                int docID = qp.LoadFromFile(fileName, "");
                int extractPageSuccess = qp.ExtractPages(1, 2);
                if (extractPageSuccess == 0)
                {
                    MessageBox.Show("Page(s) could not be extracted.");
                }
                else
                {                  
                    qp.SaveToFile(OutputFile3);                 
                }

                extractPageSuccess = qp.ExtractFilePages(fileName, "", OutputFile4, "1-1");
                //or extractPageSuccess = qp.ExtractPages(1, 1);
             
                if (extractPageSuccess == 0)
                {
                    MessageBox.Show("Page(s) could not be extracted.");
                }
                else
                {
                    qp.SaveToFile(OutputFile4);   
              }             
                qp.RemoveDocument(docID);
            }

My problem is that the second call of ExtractFile will always save the same pages from the first call.
Is this a bug or by design? I was trying to extract some different pages by each call to ExtractFile, just can not get the job done. Or I have to close file, reopen it to extract a different range of pages?

Thanks

Mark

Thanks. The idea is splitting the file into several small files, so what I did is calling the ExtractPage with different page ranges, and saving them after each call. Actually, after each call, the file is reloaded, it does gives me the right pages to save.