Chroma keying to transparency for an alpha channel?

Is there a way to chroma key to alpha? I have a clip I rendered out in Vegas that I want to take over to AE for some 3D enhancements. Some of the FX I have put on in Vegas can only be done in Vegas, so that is why I am not compositing and chroma-keying everything in AE. I need to chromakey this actor with the green background turning to an alpha channel...any ideas?

Render as AVI uncompressed (default) and select the "Render Alpha Channel" checkbox which will give you a (very likely large) 32 bit uncompressed AVI file.

Think there is a way to do this using Quicktime format as well, havn't tried though.

/magnus