1. select verts you want to lock
2. in channel box click where it says - cv's (click to show)
3.highlight the verts you want to lock
4. right click and select lock from the popup window or you can left click the channel tab and select lock.
just repeat the process and select unlock to unlock the verts
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675