Unless the instructions for the timer explicitly state that you can do this, you should assume that connecting multiple stations to one valve will eventually damage the controller.
Now many controllers have a Master Valve output. The Master Value output becomes active when ever ANY station is turned on. So if your system has only one valve, you can accomplish your goal by simply connecting that valve to the master valve output and then program all your stations as desired.
If you want only SOME of your stations to behave the way you desire, the only safe way to accomplish what you want would be to build something like a relay logic circuit. But that would likely take some circuit design and soldiering skills.
So unless you've got an expensive controller or a controller with some fancy features you just can't live without, I'd suggest finding a cheap controller with a master valve output and use it on just this one valve.