Adding a custom field onto a custom report

Hello,

I have created a custom transaction body field that is stored on one of our custom purchase order forms, it is a list of po' so we can link purchase orders together (no smarts or automation, just a filed displaying a po number).

I am now trying to add this field into a purchase order report but it is not available in the list of fields to show.

Custom field:

Custom report:

This shows me trying to search for the field name in the filed list of the report.