No you can't lock in the settings in either Shooting Banks or Custom settings Banks. Any time you change them, they're changed, that's it. Options to reload them are:
Manually - ie go through and manually reset to your starting point.
Menu Reset the Bank to Nikon's defaults and adjust from there.
Reload a saved set of settings using Nikon Capture Camera Control - this lets you load and save settings between your pc/laptop and the camera and once setup is by far the quickest method if more than a couple of settings need changing. It will allow you to reload all Shooting and Custom banks in one go - ideal for making sure you have the same settings on two D200s if you have them.