There isn't a way right now. The reason is because we didn't want to slow things down when a buyer clicked by sending them to our site to track only to send them right back to eBay. That was just 1 more thing to potentially break.
It's quite a few. A lot more than click the view sellers other items link for certain. Once we had the data we turned off the tracking. I've been thinking about adding a feature to Sellathon though that would track this. You could probably get some idea from that now. Assuming that if a buyer comes to your auction directly from another auction the only way that could happen would be from our gallery.