Sorry guys but I have to ask, Why would you want to? Once you figure it out (assuming you ever do) what you have is a sour dough bread. It seems to me that you are reinventing the wheel. There are lots of good sour dough formulae out there. Find one and go for it.
Jock has a point, but if you want to do this, you need to be a little conversant with baker's percentages, and work backwards from the final dough. You probably are going to need the firm starter to be anywhere from 30 to 90% of the weight of the flour in the dough. And the firm starter is going to be roughly equal amounts of refreshed sourdough starter and flour. Get a copy of Crust and Crumb. Reinhart changed the percentages he uses when he wrote The Apprentice, but I still like the barm in Crumb.