I've been trying but I either don't know enough about lua or it's not possible.
You can. For Example:
local TextLabel = --Your Billboard GUI Text game.Players.PlayerAdded:Connect(function(Player) Player.Chatted:Connect(function(Chat) if Chat == "/e DIE" --[[Your Command]] then TextLabel.Text = "lol help" end end) end)
That script allows everyone to change the text to "lol help" if they type "/e DIE"