Accrington Stanley midfielder Jimmy Ryan has expressed concerns about his side's defending.
Stanley conceded two late goals in their 3-2 defeat to Rotherham at the weekend and Bell knows they need to improve at the back if they are to move up the League Two table.
"We defended quite well in the game apart from those two incidents," Bell told the club's official website.
"The throw in and the cross (which led to Rotherham's second and third goals), we didn't really deal with them properly.
"We've worked well as a team but we've got to keep it tighter on set-plays. We're getting goals going forward but just not winning games because we're conceding so many at the back.
"We've got to keep digging in to get a win."