Locking the Shutter Speed

jo67

My problem is with the main dial which operates both the shutter speed and the selective AF points, subject to pressing the correct button.
I am shooting smash the cake studio sessions which are quite fast and furious, but because the cake is sometimes in front of the child I have to use the selective AF button quite a lot to get the child in focus. As they move around I also have to keep changing the AF point. I keep knocking the shutter speed and not realizing it, so that it either goes over my max flash synch speed and I get a black curtain, or I turn it down so I get blur. I simply don't have the chance to check all my settings between shots as the pace is fast.
Is there any way I can lock the shutter speed or will I just have to slow down and check the settings each time?

jo67

I can lock the quick dial ring at the back that alters the aperture but not the main dial at the front for the shutter speed?