hi,this is possible if the room is split into sections - a section for clones and vegative stage plants on a 20hrs on 4hrs off light schedule and a section for flowering with the lights on for 12hrs and off for 12 hours,your flowering section must be light tight (complete darkenss) during the 12 hour lights off period


edit - p.s. METAL HALIDE / HIGH PRESSURE SODIUM light systems is by far the better way to produce decent crops,they may cost a bit more to purchase and too run but the cost is worth it in the long run,use your cheap cfl lights for seedlings and young clones to get them started