Selected Payment Schedules Report - Need to add sort to a field value after choose statement

When we run the "Selected Payment Schedules Report", the party_name field is sort automatically.   We don't have any issues with a regular supplier but we have an issue with employee type of suppliers.  The party_name for employee is come from HR and it display as "Last Name, First Name".  When we run the "Selected Payment Schedules Report", the supplier name is display as "Last Name, First Name".  I have a need to display the party_name field for employee type supplier in “First Name Last Name” format and sort in “First name” order.  I use the below syntax and is able to display the party_name as