How do I blacklist all of the items in the workspace for Mouse.Hit?

So I wanted to make this fire blast that tracks the mouse hit position, but I do not want it to hit a part in the workspace, only the sky box. I tried doing this -

spawn(function()

    for i, v in pairs(game.Workspace:GetChildren()) do

        if v:IsA("Part") then

            Mouse.TargetFilter = v

        elseif v:IsA("MeshPart") then

            Mouse.TargetFilter = v

        end

    end

RunS.Heartbeat:Connect(function()
    if CanControl == true then

    GetMouse:FireServer(Mouse.Hit)

    end
end)

end)

But it didnt blacklist anything it still hit all of the items in the workspace.