I've searched high and low and found no article on the web in English or Japanese to explain what I could use to display some help for a function (or subroutine) in the popup that appears when entering said function in the VS2005 IDE when using VB.NET. I discovered later that you could use the XML code documentation to write the description.

Just type 3 single quotes (''') on a new line directly above the function you want to document...