title: interrupting a C# method that was called from VBA
body: <p>I have a lengthy C# calculation invoked from Excel VBA, and I'd like to allow the user to interrupt and abort the calculation with CTRL-C.  Can someone suggest a clean technique to handle this ?   The C# code is compiled as a com-visible class library and its purpose is purely number crunching.</p>
  
  <p>(Also important that the Excel session not interfere w other tasks if the user has - e.g. gone off to read his mail while waiting).</p>