Moving files into a package?

I’ve got a script that needs to move a number of files from a folder into a package application. I’m trying the following script:

tell application "Finder"
	set ProgramFolder to container of file (path to me)
	set TempFolder to (ProgramFolder as string) & "Update Items:"
end tell

try
	tell application "Finder"
		set FileList to every item of folder TempFolder
		repeat with TheFile in FileList
			move TheFile to folder "myapp.app" of ProgramFolder with replacing
		end repeat
	end tell
on error errmsg number errnum
	display dialog "Num: " & errnum & " Msg: " & errmsg
end try

Running it gives the error “Finder got an error: Can’t get item 1 of {application file “myapp” of folder “Update Items” of startup disk, document file “update.ini” of folder “Update Items” of startup disk, document file “versionname” of folder “Update Items” of startup disk}.” The error number is -1728.

Any suggestions of what I’m doing wrong?

I’ve done some more testing, and rewriting part of the code gives a more informative (but still incorrect) error message.

tell application "Finder"
	set ProgramFolder to container of file (path to me)
	set TempFolder to (ProgramFolder as string) & "Update Items:"
end tell

try
	tell application "Finder"
		set FileList to every item of folder TempFolder
	end tell
	repeat with TheFile in FileList
		set AnotherFile to TheFile as text
		tell application "Finder"
			move AnotherFile to folder "myapp.app" of ProgramFolder with replacing
		end tell
	end repeat
on error errmsg number errnum
	display dialog "Num: " & errnum & " Msg: " & errmsg
end try

The error message is ‘Can’t get "Macintosh HD:Update Items:versionname’, error code -1728. Finder clearly has no problem getting the file, because if I remove the ‘folder “myapp.app” of’ part of the move command, things work fine. Is there a way I can temporarily turn a bundle back into an ordinary folder so I can move the files into it?