Fade In/out system

Hey.

I am coder. I use lua and c++ but I have no idea about MCreator procedures. Would you like to help me?

I want to make command that fades black screen in and out. Command should be something like this: /(Command) @a in 3, or /(Command) @p out 2. First is the /command, then the target (@a, @p, @s...), then in or out (Fade In / Fade Out) and last the time how much takes to fade in or out (1-...). It has to be atleast 1 second to run the command. That black screen will be the Gui covered the entire screen.

Is this possible to do?

Thank you for your help and time :)

GotorFI (not good at MCreator procedures.....)