Particle emission play and stop

How do you use the particlesystem Emission Module.
I don’t seam to be able to play and stop the particle animation.
I’m trying to make a system where while the object is turned it will emit particels and then stop when turned back. (this means i CANNOT just disable the particle system)

How you make particles turn on and off without disableing the object?

Thanks in advance and sorry for the bad english.