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//with delphi7

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Grids, DBGrids, DB, DBTables;

type
  TForm1 = class(TForm)
    DataSource1: TDataSource;
    Table1: TTable;
    DBGrid1: TDBGrid;
    procedure FormCreate(Sender: TObject);
    procedure DBGridMouseWheel(Sender: TObject; Shift: TShiftState;
      WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TWheelDBGrid = class(TDBGrid)
  public
    property OnMouseWheel;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  TWheelDBGrid(DBGrid1).OnMouseWheel := DBGridMouseWheel;
end;

function GetNumScrollLines: Integer;
begin
  SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0, @Result, 0);
end;

procedure TForm1.DBGridMouseWheel(Sender: TObject; Shift: TShiftState;
  WheelDelta: Integer; MousePos: TPoint; var Handled: Boolean);
var
  Direction: Shortint;
begin
  Direction := 1;
  if WheelDelta = 0 then
    Exit
  else if WheelDelta > 0 then
    Direction := -1;

  with TDBGrid(Sender) do
  begin
    if Assigned(DataSource) and Assigned(DataSource.DataSet) then
      DataSource.DataSet.MoveBy(Direction * GetNumScrollLines);
    Invalidate;
  end;
end;

end.