Every Addon is different, though many follow the same general approach. Some need to be "opened" (Gui.ActivateWindow) and some need to be "executed" as you have tried... There may be another variant. I'm not sure. Some can take parameters and some can't, and if they can, then the format will often vary.
There are two general approaches you can take to try to figure this out. The first is for simple stuff like just launching an addon without going to any sub pages or using any parameters.
1 - Create a favourite for the item that you want to open and then go to your %appdata%\kodi\userdata and open the favourites.xml file
2 - This method is a bit trickier but can allow you to do more difficult things like figuring out how to pass parameters. Instead of creating a favourite, enable logging in Kodi, then navigate to the plugin and perform whatever action you want to automate. Then look in the Kodi log.
Either way, feel free to post your favourites.xml file or the pertinent section of your Kodi log, if you want help on how to convert that into a valid action for VoxCommando. We will be happy to help you figure it out.
Here's a post where I used method #2. Hopefully it will give you an idea:
http://voxcommando.com/forum/index.php?topic=2236.msg19395#msg19395