expand conditional formatting from duplicates to quadruplets

Need help. Am a young secretary and new to Excel 2013 and confused by all this difficult Excel stuff. My problem is….. Have a large range of cells (e.g. 400 or more cells) which contain many different stock symbols (i.e. text) such as, AAPL or MSFT or GOOG etc.
Have learned that the built-in Conditional Formatting has a function that identifies those stocks symbols that occur as “Duplicates”. However, I need to change this from “Duplicates” to “Quadruplicates”. In other words, I need a formula that will identify those same stock symbols that occur in at least 4 or more cells within the range. In short, I want to change the built-in “Duplicate” function into a “Quadruplicates” function. Would much appreciate any help you Excel experts out there could give me. And many thanks in advance. Jamie.