My C# application allows the user to open a file with excel. It is
implemented like this:

Process.Start(excel.exe,FileName);

It seems to work fine, it starts Excel, which opens FileName and allows the
user to process it. The problem is that if Excel is already running, it opens
another instance of Excel, instead of adding it as another worksheet in the
existing instance, which would be faster. So I want to detect whether Excel
is running, and if it is, I want to open FileName as a new worksheet in that
instance. If anyone can suggest how to do this, I would appreciate it.