No way, users will see tool tip when mouse over focused control in grid. Or just grid tool tip. I solved this problem by simple way. On MouseMove event change Tool Tip of grid. The problem is that this change not applied immediately, and works not well in most cases.
Another solution - make your own ToolTip control which you can call on MouseMove. This require a lot of programming. However, this have a benefit also - it may be made multi-line :)

>All,
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>Can you have a tooltip for each cell of a grid?
>
>I want to use the MouseMove event to reevaluate the ToolTipText property to give detail information for the cell's information.
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>TIA
>
>Rex