Moving earlier shape key without affecting newer shape key position

Is there any way to animate an earlier shape key without affecting later shape keys? I want to originally set a new shape key by moving the vertices from the previous shape key’s position. However, once I have the vertices in the correct position, I do not want the new shape key to change if the previous shape key is changed. Is this possible?

Let me know if that is unclear.

Thanks so much!

The AnimAll addon gives must more versatility and allows for this kind of animation. If you are into animation and have not checked it out, I highly recommend doing so. It comes with blender and can be activated in the user preferences

Thanks to all who viewed the thread!