Lock screen without hitting power button?

[AmandaDi]

I was sure I would find the answer with a google search, but I didn't, so I came here! I got an S3 about a month ago and I love it. I just got a new case for the phone, but I am having a hard time hitting the power button. I am disabled and have dexterity issues. I can make it work to power on and off, but when I am in a rush to lock my screen I am having trouble pushing the button through my new case. Before I ditch the case I thought I would see if there is another way to lock the screen from inside the phone. Is there an option button I am missing?
Thanks!
Amanda

 

[Dmcwethy]

I'm using 'Screen Off' app. Look in Google Play Store

 

[AmandaDi]

Totally fixes my problem! I never even thought of an ap!