procedure TCustomDBGrid.UpdateScrollBar;
var
  Pos: Integer;
  mPos, mMax: longint;
begin
  if FDatalink.Active and HandleAllocated then
    with FDatalink.DataSet do
    begin
      UpdateCursorPos;
      if (DBIGetSeqNo(Handle, mPos) = DBIERR_NONE) then
      begin
        mMax := RecordCount;
        while mMax > 1000 do
        begin
          mMax := mMax div 10;
          mPos := mPos div 10;
        end;
        SetScrollRange(Self.Handle, SB_VERT, 1, mMax, False);
      end
      else
      begin
        if BOF then
          mPos := 0
        else if EOF then
          mPos := 4
        else
          mPos := 2;
        SetScrollRange(Self.Handle, SB_VERT, 0, 4, False);
      end; (**)
      if GetScrollPos(Self.Handle, SB_VERT) <> mPos then
        SetScrollPos(Self.Handle, SB_VERT, mPos, True);
    end;
end;

procedure TCustomDBGrid.WMVScroll(var Message: TWMVScroll);
var
  mMin, mMax: integer;
  RecCount, RecNo, NewRecNo: longint;
begin
  if not AcquireFocus then
    Exit;
  if FDatalink.Active then
    with Message, FDataLink.DataSet, FDatalink do
      case ScrollCode of
        SB_LINEUP: MoveBy(-ActiveRecord - 1);
        SB_LINEDOWN: MoveBy(RecordCount - ActiveRecord);
        SB_PAGEUP: MoveBy(-VisibleRowCount);
        SB_PAGEDOWN: MoveBy(VisibleRowCount);
        SB_THUMBPOSITION:
          if (DBIGetSeqNo(Handle, RecNo) = DBIERR_NONE) then
          begin
            GetScrollRange(self.Handle, SB_VERT, mMin, mMax);
            NewRecNo := Pos * (FDataLink.DataSet.RecordCount div mMax);
            MoveBy(NewRecNo - RecNo);
          end
          else
            case Pos of
              0: First;
              1: MoveBy(-VisibleRowCount);
              2: Exit;
              3: MoveBy(VisibleRowCount);
              4: Last;
            end;
        SB_BOTTOM: Last;
        SB_TOP: First;
      end;
end;