Preventing off retrieve data multiple times

Hello everybody,

Current program i use follows these steps:

-Empty cells

-Remove comments

- Fill Headers

- Retrieve Data (From the path Results (a subdirectory))

- Sort on date and time (column D)

My Problem: The programma now used retrieves every file in the subdirectory again and again.
If it has like 100-200 files it takes a very long time.

Is it possible to make a function for this that only retrieves files when the filename is not imported already? (Title is in the D Column)

Wish: a function that retrieves only the required data and skips measuring data thats already there.