How can you cry on cue?

I don't want to be an actor but I'm just wondering how can I cry while I'm playing a sad moment. I have "escaped" from all bad emotinons I had when I thought about bad moments of my life and even if I tried I saw they can't make me cry agian. Do you have anyother options? Hurting my eyes didn't work, therefore is there anything else you can do? I don't want to use glycerin because I'm not playing on a true scene. I just organize some scenes with my friend which we play them after...