>I have a grid column containing a radio button. I want a tooltip to appear whenever the mouse is over the column containing the radio button. Currently, the tooltip only occus when a cell has the focus and the mouse is over it.

Here's a couple more cents on this...
I did this using a container/label a while back, then displaying it with mousemove of column, and hiding it or changing text in mousemove of all surrounding controls (columns/form/page, mainly)...but it wasn't real smooth, and anyway, displaying tooltips outside of toolbars/webapps is kind of non-standard. I decided to use the statusbar instead, using the same technique...