remsh and run script

Help!
I'm would like to log in su - within a script an contuine to run the commands within the script. Every time I log in as su - I have to exit for the rest of the script to run! e.g.

#!/bin/ksh

su - oracle

ps -ef |grep som <--- doesn't excute command until I log out su

oracle.

Help! Thanks!

Check out this post from the other day.