An alternative way to drop-down a control from a cell is to use True DBGrid for WinForms' built-in column button feature. If a column's Button property is set to True, a button will be displayed at the right edge of the current cell when it is in that column. Clicking the button fires the grid's ButtonClick event. Drop-down a control from the cell using code inside the ButtonClick event. Also use this event to trigger any action or calculation inside the cell.

For more information, see In-Cell Buttons.