ValidateCell (windowRef, listRef, rowNum, columnNum, cellValueString)
Called when a field in an editable list (such as the detail line entry list) is about to be exitted. Row and column numbers are zero-based. IMPORTANT: If you do this you should provide an explanation to the user via an alert or coachtip. Users will be very unhappy if they don't know why they can't exit a cell!
May be fully specified as ValidateCell:F_WINDID:List_Tab_Name:List_Col_Name:type
on ValidateCell:F_TRANS:By_Item:Qty:DI(windowRef, listRef, rowNum, columnNum, cellValueString)