Police say a masked man entered bookies on the Woodstock Road at about 9.15 am “via the ceiling of the property”.
He demanded money from the female worker.
Investigating officer Detective Sergeant Mason said: “The male then used what is believed to be a stun gun on the female twice before making off from the scene.
“The man was described as being six foot tall, wearing a black balaclava, navy sweatshirt, black trousers and carrying a navy holdall.”
Detectives are appealing to anyone that may have witnessed any suspicious activity in the area at the time to contact them on the non-emergency number 101.
Alteratively they can contact Crimestoppers and speak to the anonymously on 0800 555 111.