DB Folder: count sum of the specified rows

Hi guys, I am not an expert in DB Folder formulas, so I hope you can help me with the following (conceptually) not very difficult task. I have the table with the courses:


At the moment you can see that the standard “sum” function counts credits for all the courses given. However, I want some formula in the bottom field, that also counts the sum, but only of the courses with the property “status” being either “done” or “approved”. Any ideas? Thank you!