Will you attend the meeting “held 还是to be held”next Sunday?

Will you attend the meeting “held 还是to be held”next Sunday?
为什么?
那这个：only if the treasure box “hidden还是 to be hidden ”somewhere is found,you can wiin the game.
那如果是过去呢？

Will you attend the meeting to be held next Sunday?因为还未举行,to be 表将来
only if the treasure box hidden somewhere is found,you can wiin the game.不用不定式,因为这里指一般的情况或通常的情况