Shape keys, reset vertex position

After modification of custom shape key for mesh, we can only delete and recreate new shape key to restore vertex position from base shape key. But if i want restore position only for few vertexes, and if delete shape key layer, i was lost my work for other vertexes, this is very sad when i work with complex mesh like a character. Need some function to able reset shape key for selected vertexes to base shape or relative shape.