How to track down an External Field

I ran across an Extenal Field that I may want to modify, but I don’t know how to find it. Does anyone know the process for finding an External Field. Here’s a screen shot of what I’m looking for.

If by finding, do you mean finding the table containing the field? The DB Field is blank so this is not a database field; it is likely a dynamic field that is only calculated and displayed within the application but not stored.