Keep at it!
Take a look at the inexpensive optical rangefinder that works by aligning the image. Go out to a football field and set the element at 20 yards with a target or a friend and your set! Then range several trees, bushes, dirt clods, corn cobs, sticks ... well you get the idea and you have know yardage markers.
Good Luck!
Greg
"Getting close to the game is the joy of Bowhunting for me, the harvest is a bonus."
Live 15 ft Python after eating a small Antelope!