James,
I think it is related to the standard behavior that Windows provides to the tooltip class. They relate the tooltip to the mouse movements. Maybe there is a message to be sent to the tooltip that forces its inmediate display.
But after reviewing Samir's screenshot, I think that a different implementation may be taken. I would display an overlapping bitmaps with all the "simulated" tooltips on it. Similar to samples\newhelp,prg implementation.