Adding pop-up to list box entries? HELP

[WrldIntlR]

Ok so here's the deal. I have a list box that pulls its information off of a central spreadsheet. The entires that I'm getting often have line breaks and all kinds of nonsense. I've managed to handle that, but now my issue is that the individual list box entires can only be one line, and i have no way of fitting the entire value into the allowed space. What'd I'd like to do is that when the user mouse-overs the list box entires, it pops up the entire value in a context box.

Is this possible?

Thanks!