As long as your axes are started at the same time and the travel velocities are constant between the two captured positions you could calculate the time between these positions.
You could also connect the trigger signals also to two digital inputs of the 7358 and poll these inputs in software but in this case the accuracy won't be better than approximately +/- 10 ms.
Both methods are not very accurate but it depends on your application if you can use them. If these options don't work for you, you will need some additional hardware like a PCI-6601 counter board. This board provides a feature called "two edge separation mode" which measures the time between two different trigger signals which is exactly what you need. The timing accuracy of this board is 50 nano seconds.
I hope this helps,
Jochen Klier
National Instruments Germany
