The previous question on that very same question:
I understand.
What if your user drop a file named Thumbs.db ?
Or Desktop.ini or…
I am sorry.
You may refector your application and simply display all files in a ListBox and let the user choose from there the files (s)he needs to work with.
Doing so avoid the file type current mess (by pass it).
You only have to use a folder and load its contents by iterate it (For i = 1 to File_Count…)