Dear Mada,
There is a link below which may be suitable:
http://digital.ni.com/softlib.nsf/954feaeea92d90918625674b00658b83/8b42f71d112c202a86256b8a006b3d5d?OpenDocument
I know that this is for motion but it gives you an idea how to trigger accross the RTSI bus.
Kind Regards
LouisP
Applications Engineer
National Instruments