Saving passwords with keychain access?

how do i save the passwords and usernames entered in textfield1&2 to keychain access?

here is what i got

set itemname to "Login" as text
		set usrname to textField1's stringValue() as text
		set passwrd to textField2's stringValue() as text
tell application "Keychain Access"
			tell application "System Events"
				keystroke itemname
				keystroke tab
				keystroke usrname
				keystroke tab
				keystroke passwrd
				keystroke return
			end tell

i already have the “New Password Item” (Command + N) open,
but i just want it so it creates it with out it being open


Keychain Access scripting is dropped in Lion, I recommend to use a Cocoa wrapper for Keychain Services
like EMKeychain