Hi! I am modelling a helicopter but I have run into a problem. If you look at the file. I have projected a curve on the front of the helicopter, the curve that will be used for triming the front wind shield. _I projected the curve on the nurbs surface. Now I want to trim the helicopter body. So I select the wind shield and pressed enter so that the the helicopter body gets trimmed and that I am only left with the windshield. I am have done this 100's of time but frot some reason this command is not working.I keep getting the following error-

Warning: Trim: changed to keep originals on; curves on surface have construction history with the dependancy on the surface itself :-(
I did delete the history. Anyway PLEASE take a look and please tell me what I am doing wrong.
I want to delete the body and keep the front shield. Thanks

https://www.nitindesign.com/finalHELI.mb