if the method is to be made void, then it cannot have a return statement, all it can do is set the value. Your SeatReserved variable is already a global variable, so what you have in the last post will work, it is known as a set or setter method. All

modelsim 仿真使用说明，重点介绍前仿真和后仿真的设置方法。-modelsim simulation instructions for use, and focuses on the set before the simulation and post-simulation method.