Can we route approvals to username populated on contract DFF?

Summary:

We have a scenario in which contract creators will be selecting contract approver from the contract header DFF. we have created DFF to populate usernames of employees. Is there a way in which we can dynamically assign approval to the user who's name is populated in the DFF? We are facing challenges while routing approval to the username in DFF as we are getting only null values in the approval routing and not able to assign approvals to any users.

Content (required):

We need to assign Contract approvals to the username populated in contract header DFF

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