How to include PO Line attribute as measure to use in tables?

Summary:

Hi I would like to use the PO line attribute Suggested Dock Date value as the planning bucket value in scheduled receipts measure in the Material plan table. How can i create a custom measure with suggested Dock date as a value from PO in the planning tables

currently the scheduled receipts measure is displaying the value based on Old due date value in the PO. Instead of old Due date we need to use suggested dock date.

We planned to go with custom measure. But in Expression we cannot see the PO line attribute values. How to add those?