How do I resize a brick in one direction via a script?

I am essentially scripting a drop-down screen that hangs from a roof.

Collapsed Data: Position: -37.907, 29.45, -175.686 Size: 46.2, 0.1, 0.514

Expanded Data: Position: -37.907, 20.55, -175.686 Size: 46.2, 22.1, 0.514

Below is my thought process. I've tried using various for loops, but I have run into the issue of the part expanding in both directions, whereas I only need it expanding down and back up. The button referenced is a GUI button that acts as a toggle.

--[[

    Coded by: wattleman
    Date: 09/10/2018

    Purpose: To lower/raise the screen (change the size).

--]]

debounce = false
print (debounce)
if(not debounce) then
    debounce = true
    --Variables 
    screen = game.Workspace.SlidingScreen.Screen
    button = script.Parent

    --Functions

    function switch()

        if screen.Size == Vector3.new(46.2, 22.1, 0.514) then -- Checks if the screen is lowered, else, lower the screen.
            slideUp()
        else
            slideDown()
        end

    end

    function slideUp()

        --Raise the screen.

        button.Style = "RobloxRoundButton"
    end

    function slideDown()

        --Lower the screen.

        button.Style = "RobloxRoundDropdownButton"
    end


    --Final
    debounce = false
end


    --Trigger
script.Parent.MouseButton1Click:Connect(switch)