Mine

procedure TForm1.StringGrid1SetEditText(Sender: TObject; ACol, ARow: Integer;
  const Value: string);
begin
  if ( ARow = StringGrid1.RowCount-1 ) then                 // if Row = StringGrid1.RowCount-1 (because I have 1 static row
    begin                                                   // then I add 1 to StringGrid1.Rowcount
      StringGrid1.RowCount:=StringGrid1.RowCount+1;
    end
  else                                                     // if the above is false
    begin
      if StringGrid1.RowCount > 8 then                     // and StringGrid1.Rowcount is more then 8 then I take 1 from rowcount
        begin
          StringGrid1.RowCount:=StringGrid1.RowCount-1;
        end;
    end;

end;