How would you use non verbal communication in "Alex missed his visit last month?"
Without more information, it is hard to know what you are asking in this question. Because you have placed it in the Law group, I assume that it refers to some sort of probation-type situation in which Alex is expected to make a monthly visit to you as an authority figure. He has missed a visit and you have called him in.
In this case, your non-verbal communication will try to convey the seriousness of what he has done and the possible ramifications in might have for him. You will be formal in your postures. You will not lean back in your chair. You will not stand up and lean against your desk. Instead, you will sit straight in your chair or possibly lean towards Alex in a fairly aggressive way. You will have facial expressions that are stern. You may use gestures that are short and curt.
You will do these things assuming that you think that Alex needs someone to "lay down the law" to him so that he does not continue to miss his visits.
If this is the wrong scenario, please ask again, providing more detail.