MTM_QueryNoCellSelection

This message is sent when the table is in cell mode and a cell is about to get selected.
A cell may get selected due to one of the following circumstances:
- a keyboard action
- a mouse click
- a call to MTblSetCellFlags

Parameters
wParam
Column handle of the cell which would get selected
lParam
Row number of the cell which would get selected

Return
If a value != 0 is returned, the cell will not get selected

Beware: Don't call any function that would change the cell selection directly or indirectly within the handler of this message - the results were unpredictable!