I need an expert in Fortran and Octave

I'm a zain who has written quite a few Octave programs. In an effort to speed up those programs, I've translated many of them into Fortran. Octave has a native function called "ismember", but Fortran doesn't. In order for many of my programs to¬¬¬¬ work, I had to build my own Fortran version of ismember. Unfortunately, my Fortran version is considerably slower than Octave's version. For this reason, I'm looking for someone who will build a Fortran ismember function that is, at least, as fast as Octave's.