Locking iphone without screen turning off?

Is there any way of being able to lock my iphone without the screen going black? The top button and home button are no long working on my iphone and I can't afford to get them repaired right now. Because of this I can no longer lock my iphone which means I have to have it on home screen all day, meaning alot of unwated texts/tweets/photos happening. I try carrying round my charger but it's an inconvinience having to find a plug all the time as my work eans I'm always on the go and outside. so is there anyway of being able to lock my phone but not so the screen switches off completely? :S