I am writing a program that checks for user data input errors in certain spreadsheet cells. If a cell is in error, the program changes the cell's background color to red.

This works fine.

I now want to give the user the capability of mousing-over a red cell, and having the program then respond with a popup explaining the reason for the error. But if the user mouses-over a non-red cell, no popup is to appear.

User mouse-over would be an asynchronous operation -- that is, mouse-over could occur at any time after a cell turns red. This means that:
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1. The program must recognize a mouse-over.

2. The program must read the row/column coordinates of the cell.

3. The program must check that the cell's background color is red.

4. The program must then format the appropriate error message, and pop it up close the the moused-over cell.

5. The popup must disappear when the user moves the mouse cursor away from the cell.
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Is this (or something like it) doable?

--
Ian