Compare Columns For Name Collected From User

The attached file contains a list of customers from 2 years in column A and B respectively. I want to write a sub that takes a single argument customerName(a string variable) and it checks whether the customer is in both lists. If so, I want it to display a message and bolds both instances of the customer's name. Otherwise, I want it to display a message that the customer's name is not on both lists. I also want to write a sub that uses an input box to ask for a customer name, then calls the original sub with the customer's name as the argument.