exec() IIS 5 php

Hello, I'm running php 4.3.4 on IIS 5 with ISAPI. I want to execute a script which open Matlab (mathematical software) and then open a specific file into matlab. Everything works the way I want on the serveur through the command line php.exe. However, with a php script through a web browser the following happens : the progress bar hangs for ages and if I go to the task manager I see matlab using the memory but no CPU time (only the 2-5 first seconds). I would like to know if someone has already used the exec() function on IIS. It works fine with exec and a batch, but not with exec and another script. My script is like this ***************************************************** <?php echo "Starting the program!!!"; $cmd = "\"C:\MATLAB6p5\bin\win32\matlab.exe\" /nosplash /nodesktop /r -c E:\\SSN\\cognetics\\amp_fit_power_with_mex\\test2.m"; exec($cmd,$output,$rv); echo "program started!!!"; ?> ****************************************************** Any help, even not related to matlab will be appreciated. I'm really desperate to make it work one day Thanks