help with a container that fills up 20 minutes after being opened

I would like to make a container block which is filled with items and which fills up again with items, 20 minutes after its opening. But I can't make a procedure that is created when the block is placed (so that when a player opens it, 20 minutes later there is new stuff) and that is linked to each new block. could someone help me? (I am French and I use google translate)