This is probably what you're doing but just in case:
1. Close door and turn ignition on.
2.Fully open front window.
3. Fully close front window. Hold window button in up position for at least 5 seconds after window is closed.
4. Repeat for remaining window.
No luck tried holding up down etc but nothing. Im sure when I got the car and before I disconnected the battery to change the steering wheel it worked, but not 100% sure. The car is a december '94 build - will it have the function as standard?