Auto-Formatting Cells With Dates that are Older than 30 days

Hello, this is my first post!

I work for a company that ships products to a bunch of different retailers. I am trying to set up an excel sheet where I input the shipping information, including the date of the shipment and the name of the retailer. For instance, the Date is in Column A and the Name of the retailer is in column B. I wish to set up a formula that automatically highlights any cells in row A with dates that are older than 30 days. However, if the name/value in column B is identical to another cell within that 30 day time period, I dont want it to be highlighted. i.e., i only want to be alerted to retailers that havent ordered within 30 days. Any help would be greatly appreciated!