Make an action on every new file in directory - file-handling

Question

I have a directory with 14.000 files. 20-50 files will be added everyday to this directory.
I want to perform an action on all new files placed in this directory and I only want this action to be performed once per file.
I aldready made a rutine and it works but it really sucks.
It goes like this:
Get all files in direcroty to a Listbox
Load textfile with all processed files to another Listbox
Compare Listboxes and extract all new files.
Perform action on the new files.
Save textfile with all processed files.
This is the code for no. 3:
for i := 0 to FileListDir.Items.Count - 1 do
if FileListHandled.Items.IndexOf(FileListDir.Items[i]) = -1 then
FilesNeedHandling.Items.Add(FileListDir.Items[i]);
The rutine takes about 30-35 seconds to complete.
2 Questions:
How can I make my rutine faster ?
It is possible to get only the "new" files in the directory without using my rutine.

Answer 1

"find" command can be used for this.
find <path of directory> -mtime -1 -print
This prints files modified under the given directory within the past one day
find <path of directory> -mtime -1 -exec <command> {} \;
This finds the files modified within the past day and runs the given command on each of the files
find <path of directory> -mmin -60 -exec <command> {} \;
This handles files modified within the last 60 minutes.

Answer 2

Okay, this is not Phyton but Delphi (the tag was removed?)
I had to rethink it all, again. And this time I sucseeded.
I wrote my own rutine to load files into a listbox and made a bubble sort on it.
After that I could extract the filenames not handled.
Test scenario: 4628 Files
Test profiling goes like this:
Load filelist into:
TFileListBox Time: 2,24
TFileListBoxEx Time: 1,52
TJvFileListBox Time: 59,28 (Wtf is wrong with the Jvl libralies?)
Own rutine to load files with datetime info and bubble sort into:
TListBox Time: 1,61
// Get files list
if FindFirst(C_MailIncomingDir+'\*.eml', faAnyFile, Rec) = 0 then
repeat
Setlength(FileList, Length(FileList) + 1);
Setlength(DateList, Length(DateList) + 1);
FileList[High(FileList)]:= Rec.Name;
DateList[High(DateList)]:= FileDateToDateTime(Rec.Time);
until FindNext(Rec) <> 0;
FindClose(Rec);
// Sort
// Bubble sort
repeat
Done:= True;
for i:= 0 to High(FileList) - 1 do
if DateList[i] > DateList[i + 1] then
begin
Done:= False;
TempName:= FileList[i];
FileList[i]:= FileList[i + 1];
FileList[i + 1]:= TempName;
TempDate:= DateList[i];
DateList[i]:= DateList[i + 1];
DateList[i + 1]:= TempDate;
end;
until Done;
// Show in list
FilesInDir.Clear;
for i:= 0 to High(FileList) do
FilesInDir.Items.Add(FileList[i] + ' ' + DateTimeToStr(DateList[i]));
By sorting the files by datetime, it is possible to diff out all files not already handled with this line (0,06 instead of 10 secs for 4500 files):
for I := FileListHandled.Count to FilesInDir.Count-1 do
FilesNeedHandling.Items.Add(FilesInDir.Items[i]);