Unfortunately, ball point is really hard (if not impossible) to remove completely from leather. There are a few tips in various threads in the Louis Vuitton FAQ subforum.
This may be controversial, but I got a penmark off one of my leather bags with acetone (nail polish remover). The acetone made the area a little dull, but the pen mark came off. I then treated the area with leather conditioner.
I've read of people using hair spray or a little rubbing alcohol on a swab, please be very careful and try a tiny area first to make sure the leather is not damaged, good luck!
I don't have experience with ballpoint pen ink, but I've removed house paint from Empreinte before. I used my husband's Connolly Hide Care. I figured if it's good enough for the interior of his car, it's good enough for my bag!