在所有正在运行的emacs实例中执行命令

I have two VNC sessions where I access same projects. I have multiple emacs sessions open for multiple projects. After saving my work on VNC1 and when using VNC2, I would need a way to run a command "update all opened files" in each emacs that is running on VNC2 so it sync up with changes happened in VNC1.I have two VNC sessions where I access same pro