You're probably not going to get a speed boost over $findfile() from a DLL (assuming you're using $findfile() the correct way, and having it do the looping for you, rather than putting it in a while loop, which you should never do)
However, it would undoubtedly be faster to just write straight to the listbox rather than writing to a text file and then using /loadbuf.
Long story short, there's no need for a DLL here.
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