help - our display on Macbook doesn't want to stay lit.

help - our display on Macbook doesn't want to stay lit. So we have to hit the brightness keys - F1 all the way down till it's off then F2 just once - which makes it flash - then back down to off then try F2 brightness again - and after multiple attempts it will eventually start to brighten - then goes black again - but by repeating this procedure it eventually stays bright longer each time until we can work on the laptop for awhile. Once the computer goes to sleep, this problem starts again (sometimes but not always)