How to Whistle With 2 Fingers!

I have been to many sports events and rock concerts in my day but there is one thing that I have always wanted to learn how to do...to whistle with 2 fingers! I was watching a baseball game Monday night 7/8 and you could hear the whistling coming through the TV and i thought, "how does someone learn how to do that"?

Well I found this video that shows you how to do it! I still can't seem to get it!