title: alternative spreadsheet for real time data
body: <p>I am looking for an alternative spreadsheet to Excel, preferably but not necessarily open source, that allows a programmer to create a plugin that can update cells in the sheet from an external data source in real time. The spreadsheet would then internally compute all dependent calculation chains upon change of value. </p>
  
  <p>This is similar functionality to what the RTD method does with Microsoft Excel. The rate of external data change could be moderate to high (whatever such relativistic terms mean).</p>
  
  <p>Also the reverse process would be useful, i.e. detecting a change in cells and then sending that information to a plugin that can communicate with external processes.</p>
  
  <p>Any recommendations or experience in trying this?</p>