How do you match a transaction where a bill and an invoice have been netted and a check is issued?

How do you match a transaction where a bill and an invoice have been netted and a check is issued?

We issued an employee reimbursement in the same month as an employee purchased an item from us.  Rather than having the employee cut us a check and then writing a check back for the full reimbursement, I netted the two amounts -- thereby reducing the reimbursed check by the balance owed the company.  But now I cannot match the transactions.  It seems like a simple thing, but I cannot figure out how to handle this situation in the software.  
 

Thank you!!!!!