How to extract string from a file in inno setup

Hi All,

I'm creating a installation setup which is contains ports specifications. i.e in which port the application need to be run. In that i want to check the given port is available to use. Hence i wrote a *.bat file using innosetup which contains the command 'netstat -o > output.txt'. Im able to create the *.bat & output.txt files successfully. Now the problem is i dont know how to read that file line by line and check the given port is listeing state or in some status.

Can any one tell me how to find the string in file with innosetup? urgent..

Thanks in advance,...

Regards,
Prince