Shell Programming and Scripting

I have a ksh script, which pbruns into another account.
I want to pbrun run into that account, and continue running all the engine commands(i.e setroot, setsite xxx, etc) in my script.
But instead, it pbruns into the account, and just gives me a shell prompt.. and stops there.
Only once i exit that shell prompt.. Does it continue running the rest of the script.

I have tried to run a command with the pbrun command (e.g. pbrun –u hci tcsh ).

I have tried to run the command in the background (with the &), I have tried to pass it with -b, -c, but nothing seems to work.

Any suggestions would be deeply appreciated!

Code:

su - pbuser -c "nohup /path/pbrun -u hci tcsh &"

?

Thanks for quick response, I do not have root access to run command su.

Insted ,I'm using Pbrun to login in to hci then run nning tool commands.

I have a starup script Since a reboot and root acces is required for test.
\
su - hci -c "setenv CL_INSTALL_DIR /Volumes/app/......."

Please suggest how to excute my main ksh commands after login into another account without getting into the prompt.