Option for users to turn off Auto-Scroll in CHAT

Is there a way to turn the auto-scroll Off by each user? I bought this chat to research it for friends who may eventually have several hundred users at a time. If everyone is chatting, the messages tend to scroll too quickly. If not is there anyone you know i could pay to implement this? My friends had it in an old chat function that had a button so each user could turn autoscroll on or off.