How would I go about creating a global Gui?

When something changes for one person, it changes for everyone. Say I input something in a textbox and press a textbutton, that textbutton would send the data to other players and change there

Here is a small little example, I know it's buggy but it's basically what I am trying to do?

function _G.SendData()  --Initiates when they press the button.

Object = Instance.new("TextLabel")
Object.Parent  = game.Players:FindAllChildren("PlayerGui")
--Declare design here

end)

I'm guessing this is what it's called for a global Gui

I have also ran into another problem.. This button script is in a local script in the Player Gui.

Would I do a global function or variable?

_G.SendData() --Like this?