Using Chdir in MPI parallel programming in fortran 90

I have am MPI parallel program written in Fortran 90, where for each run, I want to change to different directories. For that I am using "system" which is inside included in MPI parallel code. But the program is not changing its directory to the assigned 6 different directories for each parallel program running simultaneously. Also I tried using "CHDIR" command of Fotran 90, but that command is returning some error. Please suggest me a better way to change to different directories in MPI parallel program in fortran 90.