How to tween playback speed?

So uh I tried to make something like that:

-- \\ Variables
local PowerOut = workspace.PowerOUT
local PowerRes = workspace.PowerRESTORED
local Prompt = script.Parent.ProximityPrompt
local Led = workspace.PowerStation.Buttons.Led
-- //

-- \\ Main


Prompt.PromptButtonHoldBegan:Connect(function(plr)
    local char = plr.Character
    local Humanoid = char.Humanoid
    local Anim = Humanoid:LoadAnimation(script.Animation)
    Anim:Play()
    workspace.PowerUP:Play()
    wait(2.2)
    repeat wait(3) workspace.PowerUP.PlaybackSpeed = workspace.PowerUP.PlaybackSpeed + 0.10 until workspace.PowerUP.PlaybackSpeed == 1
end)**

This will work? If no, how do i fix and do that ?

In other words.. i want to make playbackspeed goes to 1 smoothly and then stop.