A question in the VSX forum has intrigued me enough to test a creative solution: to intercept a command execution to re-execute it with an input parameter that you can retrieve when the execution finishes. This can be useful in a scenario where a command can be executed asynchronously twice and you want to know which/when each execution is finished:

HOWTO: Pass parameters programmatically to a command from a Visual Studio add-in
http://www.mztools.com/articles/2014/MZ2014025.aspx