Click to Expand List of Customers

I need you to add a rollover effect to my link and then on-click it needs to open a box below it and display the customers name I give you in the order they are in below in columns, 65 names per column, I have about 400, so there will be 5-6 columns. This needs to be done within 30 mins, I have an example. Quick and easy for someone who knows coding.