This event occurs when the user left-clicks on a bitmap contained in a grid control. EVENT-DATA-1 contains the column number of the cell clicked, and EVENT-DATA-2 contains the record number of that cell. For convenience, the properties X and Y are set to match these values for the duration of the event.
If you set EVENT-ACTION to EVENT-ACTION-FAIL, the normal action of left-clicking in a cell is prevented (that is, the cursor is not moved to that cell).