I need help with a custom chatbar?

So, I am making a custom chatbar, I am making my own custom chat, but I want the scripts to be SEPERATE. I know I need to use the player:chatter even but nothing I do seems to work. I've expiremented with using keys fro scripts, but they don't seem to work either, like this for example, this is a toggle script for a gui:

local mouse = game.Players.LocalPlayer:GetMouse()

mouse.KeyDown:connect(function(key)
    if key:byte() == "115"  then 
        script.Parent.Visible = not script.Parent.Visible
    end
end)

What am I doing wrong, and how can I use this to make a chatbar?

Here's an example script I guess of a chatbar, it's from a custom ChatGui I am looking at, is there anyway something similar to this could work?

function Chat:CreateChatBar()   
    self.ClickToChatButton = self.Gui:WaitForChild("ClickToChat")
    self.ChatBar = self.Gui:WaitForChild("ChatBar")
    self.ClickToChatButton.Visible = true
    self.ChatBar.Visible = true
    local mouse = game.Players.LocalPlayer:GetMouse()
    mouse.KeyDown:connect(function (key)
        if key == '/' then
            self.ClickToChatButton.Visible = false
            self.ChatBar:CaptureFocus()
        end
    end)
    self.ClickToChatButton.MouseButton1Click:connect(function ()
        self.ClickToChatButton.Visible = false
        self.ChatBar:CaptureFocus()
    end)    
end

I know this sript wouldn't work at all, and I do not want a "ClickToChat" overlay ontop on the Chatbar. I just want you to be able to press enter or something afterwards so that it automatically updates.

Thanks!