Hello Mark,

Thank you very much for all your help!

I ended up with the following script:

-----

property script_fname : "DocComp.sh" -- your "external script" name -- by Kino, 2006-05-20

property file_1 : ""
property runtime : 0
property firsttime : "yes"
property firstfile_passed : "no"
property secondfile_passed : "no"
property filetypes : {".txt", ".html", ".rtf", ".rtfd", ".doc", ".docx", ".wordml", ".odt", ".webarchive", ".xml"}

on idle
	if runtime < (current date) - 5 * minutes then
		set file_1 to ""
		quit
	end if
	return 1
end idle

on open (droppedItemsList)
	set my_path to POSIX path of (path to me)
	set shell_scpt to quoted form of (my_path & "Contents/Resources/" & script_fname)
	
	set runtime to current date
	if (number of droppedItemsList) ≥ 3 then
		display dialog "This droplet accepts two files."
		return quit
	else if (number of droppedItemsList) = 1 then
		if firsttime = "yes" then
			display dialog "Please drop another file..."
			set firsttime to "no"
		end if
		if file_1 = "" then
			set file_1 to first item of (droppedItemsList)
			set file_1 to POSIX path of file_1
			return
		else
			set file_2 to first item of (droppedItemsList)
			set file_2 to POSIX path of file_2
		end if
	else if (number of droppedItemsList) = 2 then
		set file_1 to first item of (droppedItemsList)
		set file_1 to POSIX path of file_1
		
		set file_2 to second item of (droppedItemsList)
		set file_2 to POSIX path of file_2
	end if
	if file_1 = file_2 then
		display dialog "You have chosen the same file. Quitting..."
		return quit
	end if
	
	repeat with i in filetypes
		if file_1 ends with i then
			set firstfile_passed to "yes"
		end if
		if file_2 ends with i then
			set secondfile_passed to "yes"
		end if
	end repeat
	
	set thename_1 to do shell script "basename " & quoted form of file_1
	set thename_2 to do shell script "basename " & quoted form of file_2
	
	if firstfile_passed = "no" then
		display dialog "The first file \"" & thename_1 & "\" is not of the supported types. Quitting..."
		return quit
	end if
	
	if secondfile_passed = "no" then
		display dialog "The second file \"" & thename_2 & "\" is not of the supported types. Quitting..."
		return quit
	end if
	
	display dialog "Comparing " & return & thename_1 & return & "with " & return & thename_2
	
	try
		do shell script "/bin/sh " & shell_scpt & space & quoted form of file_1 & space & quoted form of file_2
		--set res to the result
	on error errMsg
		display dialog "An error occurred: " & errMsg
	end try
	
	set file_1 to ""
	set file_2 to ""
	set firsttime to "yes"
	set firstfile_passed to "no"
	set secondfile_passed to "no"
	quit
end open

-------

The "DocComp.sh" compares two files (of different types) with Unix diff, and displays the result in a nice (readable) rtf file with TextEdit. I will upload the result in my web site, when my friend, Kino, will give me the permission.

Thank you very much again!

Best regard,

Nobumi Iyanaga
Tokyo,
Japan