You can file a withdrawal of rejection on pleading paper or wait and file an acceptance form once you come to an agreement.
Suggest thatyou and the creditor "stipulate" to the claim's rejection and that you will file an acceptance once the matter is resolved.
If you have reached an agreement with the creditor, you can prepare a pleading that states the estate is withdrawing the rejection and then file an acceptance of the claim either in full or in part as you may have agreed. Also do a separate writing with the creditor to outline the terms of the agreement to ensure that there are no further issues with this particular claim.
As we must state: any information provided in this answer is not legal advice and your use of it does not create an attorney-client relationship.