WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Lock Mechanism Screw
Courtesy of VOLVO CARS OF NORTH AMERICA.
Fit a new screw (B) and screw it in a few turns. The lock mechanism should not come away when it is being worked on but it should be so loose that it can be moved the maximum amount.