Hi, thank you for your reply.
But what I want to do is, scrolling the sprite. For example, i have same instances of the message sprite, as shown in image attached. Actually I know the way of moving the sprites up and down by moving the scrollbar point up and down. But I cannot mask them when they go beyond the chat box.
So is there any way to simplify this? because I have read almost everywhere that masking is a difficult process and should be avoided if possible.