Thanks a lot for reply. Actually the question was more about how to get the time data in easiest and most precise way.
I attach my program where the time data are computed using the fact that interval between two frequency samples is N/fx, where N is Divisor and fx is measured frequency.
However, I am not satisfied with this VI because I am not able to set measurement task parameters (Divisor, Buffer Size and TimeOut) so that it works for full range of frequencies from zero to 18 kHz.