macbook ONLY lock when lid closes?

[Tom]

So i came across an awesome screen-saver but it requires no lock on or the screen goes black rather than having desktop picture in background. This is cool, although i need to have the lock on when i close the lid so others don't get in and delete stuff. I already know htere is no way to do this in System Preferences, but would it be possible to write an apple script or something to get it to work. If so can you tell me the basic script which i have to write BUT before you quit saying "too hard", i only mean 2-6 lines giving the main targets i have to hit. NOT the whole script. (If someone wants to though, feel free ) Thanks in Advance.