Ok, with this simple fix it worked, but I was unable to make it to use editbox instead of the label and I want to show more than 255 chars. I also want it to be a bit more fancier, so I may have to look at fancy tooltip class and see if I can use it.

Finally, two problems I described earlier make this solution not perfect :(

May be in the timer I don't need to use extra window at all but rather try to use grid's Tooltip instead. I'll play with this idea later, need to work on something else now.

UPDATE. In my quick try I was unable to make column's tooltip or grid's tooltip idea work instead of using extra window.