Thanks qwerty12!

I have full selection working but it seems that i have ran into another issue - i´m also trying to add an add/remove function to the selection using the examples provided here, but i´m running into a bit of an issue while applying it (the guide assumes that your applying this to a window with GTKtree) and i´m a bit confused with how i should apply this function to the selection. Could someone someone help me with this? (sorry for all of the complicated questions- i´m still getting use to using this )

btw, i´m trying to apply the add and remove buttons above the ¨Done¨ button - to make things a bit clearer