We need the specifics of the light, wattage etc, it doesnt sound like it will work..

Heres what i sugest you do bro, im on my 1st grow and its going good and i havent spent very much on my grow..

Go to your local hardware store, (Lowes Homedepot) and buy a 120watt MH bulb, a "bright stick" and a few Compact flourecent bulbs..(CFL) (the energy saver ones) make sure you get the highest watt CFL you can, i think 27w ones are in hardware stores....Keep the CFL's 2 inchs away and any MH or HPS bulb a foot away or it will burn your plants....you could grow with just CFL, buy a soft white one for veg and warm ones for flowering...Keep your lights on 24/7 for ahwile until your ready to flower....when your ready to flower switch it to 12/12 and make sure it's COMPLETELY dark during the 12 dark hours...to help with the 12/12 get a timer for your lights..they cost like 2$ at the hardware store..