title: Opening an existing workbook from Matlab using ActiveX
body: <p>I need to open an existing excel workbook from within Matlab using ActiveX.  xlsread is unfeasible because too slow.  After getting help from this forum (thanks!) I know that to create a new excel workbook from within matlab and fill it with output you do this:</p>
  
  <pre><code>    %# Create and NAME the output file name
      wbk=1;fName = fullfile(pwd, 'ALLSDtemp2');
      %# create Excel COM Server
      Excel = actxserver('Excel.Application');
      Excel.Visible = true;
      %# delete existing file
      if exist(fName, 'file'), delete(fName); end
      %# create new XLS file
      wb = Excel.Workbooks.Add();
      wsheet=1;
  
      (...calculations...)
  
      % Write output to excel file
      Mat=[calculation_output];
      % Select work book
      wb.Sheets.Item(wsheet).Activate();
      % Get Worksheets object
      ws = wb.Sheets;
      %# insert matrix in sheet
      Excel.Range(cellRange).Select();
      Excel.Selection.Value = num2cell(Mat);
  </code></pre>
  
  <p>But I can't figure out how to do this with an excel workbook that already exists.  And my efforts to do so caused a "serious error" in my computer the other day.  So I could really use some guidance.</p>
  
  <p>Thanks</p>