BB Curve :: Auto-locking The Keyboard In 9300?

i would like to know if there is a way, with the phone by itself or with any app, to auto lock the keyboard.In any nokia phone (the old ones, not smartphones) you can set it to auto lock after X seconds you didnt use the phone. Thats what I need.The thing is, i have the phone locked in my pocket. I recieve a call, I answer it, and when I finish, the phone stay unlocked. I forguet to lock it again, put in my pocket, and hell unleashes (phone calls, messages, and more without wanting).So, I want my phone to lock itself after 15 sefonds in stand by. And to stay locked after i recieve a call.