WatchKit Image Animation wait for finish

I currently looking for a wait to wait to finish my Image Animation and then start the next one after it is finished.

I thought to use a completion handler but it "does not work for me" is there a way to use it in that case?

if X > 1 {
            self.GroupIMG.setBackgroundImageNamed("single")
            self.GroupIMG.startAnimatingWithImagesInRange(NSRange(location: 0, length: 300), duration: Repeater, repeatCount: self.X)

        }



//this should start after the if is done

            self.GroupIMG.setBackgroundImageNamed("single")
            self.GroupIMG.startAnimatingWithImagesInRange(NSRange(location: 0, length: leftX), duration: Repeater, repeatCount: 1)