Locking Settings In Video Mode

RJJ

Hi ,
I am researching the video features of the D3100.
Does anyone know if there is a work around in guide mode to lock the aperture, shutter speed, and ISO in video mode? I am finding mixed answers on this subject. I have a T2i and I am getting way to much noise and soft mushy images. Someone wants to trade me a D3100 and some cash for the T2i. The D3100 video looks better to my eye but for shooting things like documentaries I need to know if it can be locked before considering.
Thanks.
RJJ