IsEXCELrunning

Checks if there is a running EXCEL process.

|IsEXCELrunning| returns a simple logical "true"/"false" based on whether there is an instance of EXCEL running. Since many Matlab ActX calls may bonk if there's already some instance running, this allows a check.
It also allows a "Force Kill" option to close all EXCEL processes.
This is useful because a number of ActiveX based calls used by Matlab (e.g. xlswrite) may fail if they attempt to open a COM connection while a process is already running.

(This was inspired by a Stack Exchange post by http://stackoverflow.com/users/3898611/daniel-pereira)