Is there a way to lock the shutter speed with the GH2? It's pretty annoying that you can knock the shutter speed off by accident. Sometimes I'm shooting and I see that I have mistakenly gone up or down from 1/50 because it's so easy to touch the little wheel on the top right by accident. It also happens with aperture when using Lumix lenses if the wheel is set to aperture. Is there a way to lock that wheel or at least the shutter speed somehow when in creative movie mode?