triac firing and pulse generation

Hello,

I would like to create activate a TRIAC and control its firing angle (e.g. dimmer). 

I work with a cDAQ 9178. I can generate a 50Hz train pulse with NI9472. Further I can monitor the zero crossing voltage with a circuit that I made, so that I read 0 or 5V depending on the voltage wave. My issue is that I don’t know how to synchronize the pulse generation with the zero crossing and how to change its firing angle.

I attach the VI. I can only set an initial delay but I can not refer it to something or change it later. I hope that somebody can help me.