identify the execution of a command

Is there any way to identify the execution of a command?

And do a procedure to execute a command supplement?

A practical example would be:

When you call Qsave, run and Qsave

then then display a message on the screen?

thank you

Could used the command "_.undefine" "_qsave" and define what I want within a new procedure qsave, more to lost the functionality is not good to me

I need that when a certain command is executed, I can identify that the command

was executed and run some other commands

Use a Command Reactor with a callback function triggered by the :vlr-commandended event.

Here is an introduction tutorial on reactors (from AfraLISP):

http://www.afralisp.net/visual-lisp/tutorials/reactors-part-1.php

Thanks Lee

Below the code running in the future for those who want:

(if (null *save-reactor*)
   (setq *save-reactor* (vlr-editor-reactor nil '((:vlr-savecomplete . savedrawing))))
)
(defun savedrawing ( reactor params )
   (Alert "aaaaa")
   (princ)
)

To learn more events that you can access, follow the link:

http://www.bricsys.com/bricscad/help/en_US/V12/DevRef/source/Lisp_vlr.html

the key is to change the 2 items in this command

(setq * save *-reactor (vlr-editor-reactor nil '((: vlr-savecomplete. savedrawing))))

vlr-editor-reactor and vlr-savecomplete

In my case vlr-editor-reactor to pick stocks editing the file and vlr-savecomplete to run after save the DWG file