Starting new seeds while other plant is flowering...

I have a question. I'm finishing up my first grow right now - coming along pretty darn well (should be done in 4 weeks) and I wanted to start my new grow (super silver haze & big bang) right now because I need to flower the plant by june and harvest by the end of august, due to moving.

I have my current plant under a 400w HPS lamp. I also own a 400w MH bulb, but only have one ballast and one grow room.

My question is -- Can I germinate my new plant and begin growing it under my HPS lamp on the 12/12 cycle alongside my flowering plant, or will this create problems? I also own a few flourecents, but I would like to veg my new guy under a solid lighting setup. - ...Could I switch the bulb back to MH and continue the 12/12? I'm stuck with how to go about this...

Perhaps switch back to MH on a 24 hour cycle and move my flowering plant in and out of the grow room (to a dark room) every 12 hours?

Any suggestions for what to do?

Thanks a ton.

Dude that's a stuff up.... i personally wouldn't waste my time trying to flower a seedling, im sure it would work but it would be like 1 joints worth of bud... u need to veg it for atleast 2 weeks before you go 12/12 if you want bud... is there no way u can save the seeds for your new place? or is a matter of planting them or giving them away? if thats the case, flower the blimmen seedlings and let us know what happens...

How I do it is I use my flowering room for the 12 hours and move the small plants to a closet with a few cfls for the rest of the 18 hours. Then put them back in when the 12/12 starts. Its a bit of work but it saves lots of room and the small plants still get 18 hours till they are ready to go 12/12.