Don't bump your thread up like that. It often takes hours or days to get a response. If you need immediate response, hire an expert.

chmod only sets the permission bit so it could be run. To run it you would then type:
./bk.ksh

If your interactive shell is ksh as well, it might work, but the first line really should be something like:
#! /usr/bin/ksh

but your path to ksh may be different. "which ksh" should show you the path if you don't know it. And if you have any further questions, post your version of unix which you can find with "uname -a".