My head just exploded from pool nerdiness, but in a good way I assure you.

So I can see how this is easier when I open. Test for opening CYA levels; determine what I want my final CYA to be; buy that much Dichlor using the formula above; chlorinate with that when I open until I have used up the determined poundage; then switch back to bleach to chlorinate for the remainder of the season.