You can often ignore the "related table", "unrelated table" divisions of this list when setting up a calcuation in a script step as they will refer to the context established by the current layout in your database and that may not be the current layout at the time your script executes.
You don't need the open file script step here, the entire script can be:
Go to Layout ["Study Request" (Study Request ) ]
Go To Record
If you don't have a layout based on a Table Occurrence of this external table, you will need to create one.
But you can also use import records to import data from this table whether you set up an external data source reference or not.