How to force use of GAC'd assembly?

I am working on an application that use开发者_开发技巧s an assembly that must be in the GAC. My problem is that when I update the assembly in the GAC I have to reboot the machine to get my service to pick up the new assembly. Is there some way to force services that are using a GAC'd assembly to start using the new one?

The service using the GAC'd assembly is SharePoint Timer Services. I've tried stopping and starting that service as well as stopping and starting IIS...

Try stopping the service before installing the new assembly.