How to delete goal that was used in Performance document?

Summary:

Content (required):

Our Customer determines the goals for the Employee for one year. Then these goals are monthly evaluated using Performance document.

If there is any way to delete one of the goal in the middle of this Review period or replace it by another one (after the first Performance Document was completed)?

Version (include the version you are using, if applicable):

21D

Code Snippet (add any code snippets that support your topic, if applicable):