Having trouble triming srf with Brep Intersection.

Hi,

I'm new to Grasshopper and I am trying to reproduce the National Taichung Theater by Toyo Ito and I have been following these series of exercises https://vimeo.com/66324337 to help me.   My problem arises when I try to trim my surface using a brep intersection. I have tried a few ways of trimming my surface (such as srf split) but nothing actually gets trimmed. Since I'm new to this language I cant seem to point out where my problem occurs. If some kind soul can point out where my problem arises and give me a hint of how to continue then I hope I can figure out my issue. The operation is fairly simple and I feel like I almost got it, but am still at the point where I need extra help. THANK YOU, btw I'm having allot of fun learning this awesome plug.

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