I am not sure that you will find such tool. I think that you have to write your own analysis code.

Hi Bulat!

You can do that by using the function gmx distance. Then you'll need to provide the index file for that h-bond which you want to study. gmx distance calculates the distance between pairs of particles as the function of time. You can also check gmx pairdist. On the other hand you may write your own code where you analyze trajectory by yourself. It is very easy too.

Thanks all. I solved this problem with VMD.