local cmdBar = game.Players.LocalPlayer.PlayerGui.cmdBar
local commandBar = cmdBar.commandBar
local input = cmdBar.commandBar.Input

input.Size = UDim2.new(
input.AbsoluteSize.X/input.Parent.AbsoluteSize.X,0,										input.AbsoluteSize.Y/input.Parent.AbsoluteSize.Y,0)
input.Position = UDim2.new(
input.AbsolutePosition.X/input.Parent.AbsolutePosition.X,0,								input.AbsolutePosition.Y/input.Parent.AbsolutePosition.Y,0)

Input is a child of commandBar.

I've included a model because it is really hard to explain without seeing it:

Click here to see the model!!!

Please take a look and tell me what I did wrong.

Note: commandBar does not need to be scaled, only input. However the position gets messed up and I'm not sure why. Why does it get messed up?