Help launching external file

I’m programming a button inside of Flash to execute the following applescript:

–set the name of the file to open
property fileName : “quiz.pdf”
–get the path to the containing folder
set myPath to (path to me as string)
set AppleScript’s text item delimiters to “:”
set the parentFolder to ¬
((text items 1 thru -2 of myPath) & “”) as string
set AppleScript’s text item delimiters to “”
– find the flash file try
set targetFile to alias (the parentFolder & fileName)
on error
–ie if there’s no file here by this name, it will quit.
return quit
end try
tell application “Finder”
open file targetFile
end tell

How or where do I tell the script to look into a folder entitled “pdf”? Also, will this script work for the people using OS 9.X? Any help would be appreciated!

Thanks!

Ted