Does this Xtension come with a UI, do you need to have acces to it?
If not, its a somple case of calling the appropriate shortcut menu vis AppleScript. (If there isn't one for your XT, just set one up in keboard shortcuts prefs).
If you do need access to the UI then you have to check if it is compatible with UI Scripting.
That said, there is porbably a way to do what you wish without using the XT.
HTH