(defun c:**r** nil
  (if averigua
    (progn
      (vlr-remove **a**)
      (setq **a** nil averigua nil)
      (princ "Open-file Command-line DEACTIVATED");"SensiCMD DESACTIVADO")
    )
    (progn
      (setq **a** (vlr-command-reactor "***" '((:vlr-unknowncommand . averigua))))
      (defun averigua (a b / c)
        (if (setq c (findfile (vl-string-subst "." "@" (car b))))
;;;          (decodifica c)
	  (LM:open c)
        )
      )
      (princ "Open-file Command-line ACTIVATED");"SensiCMD ACTIVADO")
    )
  )
  (princ)
)
	 
 
	Here you go.
 
	Copy this code into the acad*.lsp file where you save your custom lisps. 
	Once loaded, you can enable or disable the included code by typing the **r** command. 
	I assume you've downloaded Lee Mac's code (LM:open). 
	It's perfect for what you need, so I've included a call to "LM:open," but you'll have to add the code for this function yourself.
 
	As for the **r** command, when the included code is enabled, anything you type on the command line that matches the name of a file found in any of AutoCAD's "SupportPaths," "LM:open" will open it with the default Windows application. This will happen without any command being executed
 
	To disable the code, just run **r** again.
 
	 
 
	PS: When typing any file name, you must replace the  .  with @
 
	Example: to "acad.lsp" type "acad@lsp"
 
	 
 
	I hope it's useful