mask is the hole in my cover

[fou99004]

I have a white mc that I'm putting over everything that has an alpha of 70ish. I want my mask to be a clear hole in the white cover but I can't figure out how to do this. I've seen this done as kind of a spotlight but I can't find an example of how to do this.

Can anybody point me to a tutorial or give me a hint?

Thanks.