Sorry for my late reply but I have been busy.
And now I don't have Girder on this machine so I'm doing this by what I remember.
Start Girder. Goto preferences and select the mouse plugin.
Make sure it says "plugin loaded in memory"
Then in the file menu select "enable input devices"
Add a new command. (it will be labeled new, but you can rename it as you want).
Then click on "learn event".
Now press one of your special buttons.
If Girder recognised your special button, it will add an EvenString to your new command. Like in the picture below :
(the example is from an IR remote, but the important thing is that you see the EventString)
Can you try this?
If it works we will take it one step further.
Rafke P.