Livetype - title font is a video rather than solid colour.

Hi,

I have a question and have no clue what it would be called or even how to describe it. I am editing a video and for the title at the beginning I currently have just a white font on top of my footage. What I would like to achieve is that within the title like the characters is a separate video. So I want to apply seperate footage to the title and have it over my background footage.

I hope that makes sense, if any one has any idea how to do this or a link to a tutorial please help!

Thanks,

Scott