Calendar tooltip

Hi all,


I have a month-by-month calendar in an excel spreadsheet, that currently fills the cell with the event title (based on a table of event data). 

What I really want to achieve is that when the user clicks on the cell, a window/textbox will appear with more details of that event in. I would really like to be able to format this text box in a style that matches the calendar too.

Unfortunately, the work is confidential, but I should be able to work with the code, I just do not know how to start it. 

Many thanks
Sam