my english is poor
excuse me
i know this question is for 2016 year
but i answer it because it is may one person has this problem
when you are choosing for buttons a word from virtual keyboard of xpadder
on this virtual keyboard is a button "advanced"
click on it
you see there is a option "set selector"
you can enable it and make it until with a button switch set 2 or set 1 or set 3
you can see it on image: