Solved the problem on my own, just copied ChatManager script and edited it from: http://wiki.roblox.com/index.php?title=Custom_chat_GUI
COMMUNITY QUESTION
[Solved] Error: "Unable to cast value to Object" How can I fix it?
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You should use filterStringForBroadcast, as you're not whispering to another player.
filterStringForBroadcast makes it work, but doesn't filter inappropriate words
Also filterStringForBroadcast makes everyone text to appear as: "Click here or press / to chat." except for your own text, also everyone name in chat appears as yours.
What line are you having the error on?
FilterStringForBroadcast does work, but it doesnt cencor anything in studio.