I am working on Applescript to paste what was last copied into any current field. It should be used with VoiceOver and the key code method (only as I know) does not work all the time.
tell application "System Events" to key code 9 using command down say "paste"
I use the keys:
tell application "System Events" to keystroke "v" using command down
I don't know about the error you should get, so you have to share.