Along time ago there was a piece of plastic with lines across it where you shot in say like a 20 yard pin and a sixty yard pin then you took this piece of plastice with the lines and moved it across your top pin till both the long and short distance pins lined up with the lines on piece of plastic then you could set your other pins with other lines that were on the plastic. It actually was quite accurate. I believe Lancasters still sells them.
I went and looked and found them here is the link
http://www.lancasterarchery.com/product_info.php?cPath=39_102&products_id=2666