hmm, something could be done using Dirplus, and one of the time UDF's.
Here is something using flipctime() just because i know that one 
Code:
$files = dirplus("c:\pdf files",'/a-d /f pdf')
$startdate = '2005/12/01'
$endDate = '2006/1/01'
for each $file in $files
;change the time to 24h
$time = timeconvert(split($file.DateLastModified)[1] + split($file.DateLastModified)[2])
;reset date to yyyy/MM/DD
$date = split($file.DateLastModified)[0]
$date = split($date,'/')
$date = $date[2]+'/'+$date[0]+'/'+$date[1]
$filedate = flipctime($date, $time)
if $filedate > flipctime($startDate,'00:00') and $filedate < flipctime($enddate,'00:00')
? $file
endif
next
grab the UDFs timeconvert, dirplus, and flipctime...
