won't overwrite files

I have the following script which takes all the files in a folder moves them to another destination folder. However, If a file already exist with the same name, the script stops and won’t overwrite the file (which I want it to do). Is there a way to force it to overwrite it, or a better way to script this?

tell application "Finder"
	set Destination to ((path to movies folder as text) & "destination folder:") as alias
	set Source to ((path to movies folder as text) & "source folder:") as alias
	try
		set a_list to every file in Source as alias list
	on error -- only one item present
		set a_list to every file in Source as alias as list
	end try
	repeat with i from 1 to number of items in a_list
		set a_file to (item i of a_list)
		move a_file to Destination
	end repeat
end tell

Hi,

this is sufficient


tell application "Finder"
	set Destination to ((path to movies folder as text) & "destination folder:") as alias
	set theSource to ((path to movies folder as text) & "source folder:") as alias
	move files of theSource to Destination replacing yes
end tell