There's a few dozen ways you can do it but probably the easiest for new spellcast users would be groups.
A group is a container that holds sets. You'll notice that your xml has a group, but only one. If you make another group and call it EVA then you can then place a new set also named TP that will have your evasion set in it. When you set your group to the EVA group, it will use any set in the eva group first, and then the normal group(if it's inherited, will post code you can use that will work).
So basically here's a new set of code with an eva group:
http://pastebin.com/cJcac0jN
To switch groups, simply type /sc g eva
To switch back, type /sc g blu
Hopefully that'll help.