LaunchBar script/append text

LaunchBar has this script. I would like that it would append selected text in current application to rich text-file in hard coded location (meaning script dont ask location of text-file) and put separator between them:

old text here

----- date and time here --------

new text to here

-- Copyright (c) 2006 Objective Development
-- version 2

on run
	display dialog "This script appends arbitrary text to a text file. Please select a plain text file (with a .txt extension) in LaunchBar, press the Tab key, select the Append Text script via abbreviation search and press Return. You can then enter the text that shall be appended to the file." buttons {"OK"} default button 1 with icon 1
end run

on open listOfFiles
	set theFile to first item of listOfFiles
	set p to POSIX path of theFile
	if p ends with ".txt" then
		set defaultButton to "Append"
		set title to "Append Text:"
			set r to display dialog title default answer "" buttons {"Cancel", defaultButton} default button 2 with icon 1
			if button returned of r is defaultButton then
				set s to text returned of r
				do shell script "echo " & quoted form of s & " >> " & quoted form of p
			end if
		end try
		display dialog "This is not a text file." buttons {"OK"} default button 1 with icon 1
	end if
end open