When the meeting will be had by us will be decided by him soon .
/
When we will have the meeting will be decided by him soon.
加油!不明白再问!为什么不用It原句中没有IT 呀，注意：变被动词句是：原句中的宾语变被动句中的主语，原来的动词变被动结构（be +动词的过去分词）这不是状语从句吗？没错，整个句子是before 引导的状语从句