Hello Przemyslaw,
For Daisylab support, try contacting support from: http://www.dasylab.net/dasylab_english/
From my knowledge, it's feasable to synch to daq boards using a RTSI cable, but I've never done synchronization in two different computers. I don't think it would work, unless both computers have the same PCI bus speed. If they do have the same speed, you can try connecting them through a large RTSI cable (if they have a RTSI connection), or you can look at documentation on RTSI lines and see what pins you would need to connect.
Please let me know if you have any additional questions.
Thanks,
LA