I want to write a program in virtual worlds that uses the line follower to count lines. Does anyone know how to complete this? I've tried using while and for loops but nothing works.

If you've tried code, then please post it. It's usually better to work off of what you figured out on your own than to have someone just tell you. Have your tried looking at the relevant sample programs?

What exactly is your setup? The more info we get, the better and faster we can help out -- what does the robot look like, what does the arena look like, etc. Pictures (or in this case screenshots) would be perfect. Also, the best thing for you to do right now is write pseudo-code (description of what exactly you want the robot to do, step by step; examples here: http://goo.gl/9vE29), which will make it much easier for you to write the actual program.

EDIT: I see that magicode and I were replying at the same time, and I agree with him: also post whatever code you have.