Could you elaborate on what you mean by "dynamically set endpoint?"
What parts are dynamic?
If the endpoints are completely different, one option is to create multiple REST Connectors and set them as separate Data Sources for the Data Page, and introduce logic that chooses the correct connector for the correct situation.
Otherwise, the REST connector's ruleform should be providing you the option to make any part of the URL dynamic. You would just use a request Data Transform to set up the properties/parameters that the URL's values come from.