Paul,
There won't be a way in hardware to do this, but you could do it in software.
On the machine with the PCI-MIO-16E-4 you could monitor the PFI5/UPDATE pin. This pin pulses every time the output is being updated.
You could monitor the PFI5/UPDATE pin with a counter on the PCI-MIO-16E-4 and when the counter sees the first transition you will know that the output has started.
On the other PC, you would need a way monitor the program on the host PC. If you're using LabVIEW, you could use Datasocket or VI Server to monitor the control in the program that outputs the result of the counter. So, you could have both programs monitoring the count output and when it transitions from 0 to 1, both programs would be triggered.
There are probably other met
hods, this is just a suggestion. I hope this helps.
Regards,
Todd D.