Find or track active field in a page

Is there any way I can find or track which field is active/highlighted on a page?

On Page 950 Time Sheet I need to have some way of knowing which of the days (CellData[x]) is currently selected. More specifically I need to be able to press a button, and perform some acion based on the day that the user is currently standing on.

What have you tried so far?

Normally you would create a new button, which would be filtered to the current record/row.