How do I look in sub folders?

How can i make my script (attached below) look at the files inside of subfolders
to run my name changing script

set errorlog to ""
set nameList to read file ((choose file with prompt "Choose the data file.") as text) as list using delimiter return
set pathTotheFolder to (choose folder with prompt "Select the folder containing the files to rename.") as text
set AppleScript's text item delimiters to tab
repeat with thisNamePair in nameList
	set {oldName, NewName} to the text items of thisNamePair
	tell application "Finder"
			set the name of file (pathTotheFolder & oldName) to NewName
		on error
			set errorlog to errorlog & return & oldName
		end try
	end tell
end repeat
set errorlog to errorlog as string
set buttonResult to display dialog "These Old Items can not be found" & errorlog buttons {"clipboard", "OK", "EMAIL"}
if button returned of buttonResult is "clipboard" then
	set the clipboard to errorlog
else if the button returned of buttonResult is "EMAIL" then
	tell application "Microsoft Outlook"
		CreateMail Body errorlog Recipients "rdriscoll" Subject "These images are not in Database" without Display
	end tell
end if

thx in advance for any help

Simply check if thisNamePair is a folder. Eg:

if folder of (info for thisNamePair) then -- is a folder!

… Or:

if text item -1 of thisNamePair as text is ":" then -- is a folder!

Then, list items within the folder and repeat the loop:

set folders_contents to list folder thisNamePair without invisibles
repeat with i in folders_contents
     set this_file to (thisNamePair as text & i as text) as alias

A thypical routine for this:

repeat with thisItem in theseItems -- if theseItems are aliases
	set the itemInfo to info for thisItem
	if folder of the itemInfo then
	end if
end repeat

on ProcessFolder(thisFolder)
	set theseItems to list folder thisFolder without invisibles
	repeat with i from 1 to count of theseItems
		set thisItem to alias ((thisFolder as text) & (item i of theseItems))
		set the itemInfo to info for thisItem
		if folder of the itemInfo is true then
		end if
	end repeat
end ProcessFolder

on ProcessItem(thisalias)
	-- do whatever...
end processItem

yes this recursive thingie i have been looking for. would i have to make any changes if :

 delete thisItem
end ProcessItem

Would that cause the count number of the ProccesedFolder to get messed up if that file was instantly deleted in processItem?