Author: Jonas Bilinkevicius 

I need to monitor a series of directories, and perform a selective deletion (based 
on file date) when they reach (or go over) a certain size.

Answer:

The snippet below is a procedure I wrote to monitor a directory and take action 
when files are added to that directory. It uses these WinAPI functions to 
accomplish that purpose:

FindFirstChangeNotification
WaitForSingleObject
FindNextChangeNotification
FindCloseChangeNotification

If you look these up in the help, you may be able to solve your problem using a 
similar technique.

1   procedure TDosNotifyThread.Execute;
2   begin
3     FChangeHandle := FindFirstChangeNotification(pchar(cRequestDir), false,
4       FILE_NOTIFY_CHANGE_FILE_NAME);
5     repeat
6       FExitWait := WaitForSingleObject(FChangeHandle, cThreadCycleTime); {See GLOBALS}
7       if FExitWait = WAIT_OBJECT_0 then
8         PostMessage(MilerForm.Handle, DO_REQUEST, 0, 0);
9       FindNextChangeNotification(FChangeHandle);
10    until
11      RTQ or Terminated;
12    FindCloseChangeNotification(FChangeHandle);
13    if not Terminated then
14      Terminate;
15  end;