having problem to convert to pdf

an error occures when i am trying to do run this applescript, the message i get is that there is no such a file, i"ve seen
that the file name has an space character in the middle of the name, so unix can’t find it, how can i overcome this problem.can somebody help me please!!!


try
	set source_folder to "MacintoshHD:local:GRAPHIC:EPS_FILES"
	set target_folder to "MacintoshHD:local:GRAPHIC:JPG_FILES"
	tell application "Finder"
		set every_file to every file in folder source_folder
		repeat with this_item in every_file
				do shell script ("pstopdf " & this_item)
		end repeat
	end tell
on error error_message
	display dialog error_message
end try

thanks

Make sure to end all folders with " : "

“MacintoshHD:local:GRAPHIC:EPS_FILES:”

thanks, that not the problem, one of the file name has a space character within the name, when i do the do shell script it doesnt find the file

 set sourceFolder to quoted form of "Macintosh HD:local:GRAPHIC:EPS_FILES"

This will pass on to shell scripts a string with the special characters as a single parameter.

Craig