DbGrid постоянно моргает

procedure TLibEdit.DBGrid15DrawColumnCell(Sender: TObject;
  const Rect: TRect; DataCol: Integer; Column: TColumn;
  State: TGridDrawState);
var i,j: integer;
    Style: TFontStyles;
    holdColor: TColor;
    culc, CurrMH : integer;
begin
  Style:=DBGrid15.Font.Style;
  holdColor :=DBGrid15.Canvas.Brush.Color;
  if (DB_Module.TO_TypeL.FieldValues['LastMH']<>Null) {and (Edit5.Text<>'')} then begin
    CurrMH:=StrToInt(Edit5.Text);
    culc:=DB_Module.TO_TypeL.FieldValues['LastMH']+DB_Module.TO_TypeL.FieldValues['TO_T_Period']-DB_Module.TO_TypeL.FieldValues['TO_T_Tolerance']; 
    if (DB_Module.TO_TypeL.FieldValues['LastMH']=Null) or (CurrMH>=culc) then begin
      DBGrid15.Font.Style:=[fsBold];
    end;
  end;
  i:=0;
  j:=high(TOTypeArr);
  while (i<=j{high(TOTypeArr)}) and (DB_Module.TO_TypeL.FieldValues['TO_T_ID']<>TOTypeArr[i]) do begin
    i:=i+1;
  end;
  if (i<=high(TOTypeArr)) and (DB_Module.TO_TypeL.FieldValues['TO_T_ID']=TOTypeArr[i]) then begin
    DBGrid15.Canvas.Brush.Color:=clLime;
  end;
  DBGrid15.DefaultDrawColumnCell(Rect, DataCol, Column, State);
  DBGrid15.Font.Style:=Style;
  DBGrid15.Canvas.Brush.Color:=holdColor;
end;

procedure TLibEdit.DBGrid18DrawColumnCell(Sender: TObject;
  const Rect: TRect; DataCol: Integer; Column: TColumn;
  State: TGridDrawState);
var i: integer;
    holdColor: TColor;
begin
  i:=0;
  while (i<=high(TOArr)) and (DB_Module.TO_Ty_Op_TBL.FieldValues['TO_O_ID']<>TOArr[i]) do begin
    i:=i+1;
  end;
  holdColor :=DBGrid18.Canvas.Brush.Color;
  if (i<=high(TOArr)) and (DB_Module.TO_Ty_Op_TBL.FieldValues['TO_O_ID']=TOArr[i]) then begin
    DBGrid18.Canvas.Brush.Color:=clLime;
  end;
  DBGrid18.DefaultDrawColumnCell(Rect, DataCol, Column, State);
  DBGrid18.Canvas.Brush.Color:=holdColor;
end;