Sohail...I have posted reply to rejection letter.We are in same boat and INSHAALLAH we will pursue our case till the end.Following steps i took in order to post reply.

1 down load challan form FPSC web site and deposit fee in NBP
2 write an application to secretary of FPSC in which present the arguments
3 Also mention that you want to personally appear before commission
4 don't forget to sign your application
5 application,copy of rejection letter,receipt..all three must be posted. do
all this before 30 days.Please remain in contact with me.If we feel need to go to high court,we will do this together.