Is there a way to show detailed data (i.e. concatenated from other columns)
in a pop-up box - either by clicking or rolling over a cell?

For example, when a user rolls over or clicks cell E5, I'd like a popup
ballon/box to display cells T5, U5, V5, W5, etc with line breaks after each.

I've searched and found solutions for displaying help messages (e.g.
validation input message) or pictures, but not data. Thanks for your help.