I just recently made this and have only used it a couple of times, but it seems to be doing the job. I decided to use up my store-bought detergent tablets first just so that I didn't have them hanging around taking up space in my pantry.
3 cups Borax
3 cups washing soda
1 cup LemiShine (for hard water issues)
Mix all ingredients together. Store in sealed container. Use 1 tablespoon per dishwasher load. (I just fill my little receptacle rather than measure it out.)