hello, my question involves a litigation issue where a plaintiff is suing two people personally for returned checks.

the checks involve a business transaction where a longtime friend/manufacturer gave me goods for sale and in return requested "promissary notes" for payments in the future. the manufacturer had a ongoing account with us where he was paid. the promissary notes were in the form of business checks which were left blank in the dates intended for not depositing rather security for the recipient. the manufacturer when ahead and wrote in the date without consent and deposited the checks. of course, for the large amounts, they were returned nsf. he has now sued me for the checks. i have agreed that i owe him the money, but he is seeking liens. i am seeking a payment plan. can i stop him from doing that, and showing that the judge that the check was tampered? thank you