Hello, Please can someone help me with some conditional formatting that I am stuck on?

I have a spreadsheet that monitors complaints received from customers. In column H, I have the date on which the complaint was logged. In column Z I have the category of the complaint. I need to format the cells in column Z to highlight red if that specific category appears in the column more than twice within a 30 day period. I'm not sure how to write the formula in CF so that I can apply it to the entire column. So, the purpose of this is so that I can recognise if a trend is occurring and a specific category of complaint is occurring more than three times within a rolling 30 day period. I hope this makes sense. Any help much appreciated.