Make a small, invisible box centered in the middle of the carousel. Then make a Global Variable for CurrentSpriteUID, with the value set to 0. Then make it to where when Sprite is overlapping the box, set CurrentSpriteUID to SpriteUID.
Then on Left Clicked with condition "If CurrentSpriteUID = the UID of the designated sprite," it will take you to the specific URL you assigned to that sprite.
It will work like this: https://dl.dropboxusercontent.com/u/172450407/LevelOneSoFar/index.html
(press Q and E when you are on a tree, and the tree is at 65% opacity. Move with WASD.)
I have the "purple" box linked to a build command instead of a URL. When you are on "purple," left-click.