Shell Programming and Scripting

hi i need to perform following task
have to write script to display menu
like 1) login as user1
2) login as user2
3) login as user3
4) go to shell
script will be run through root user user1, user2 will be logged to specific thr account. if 4th option selected it must pass control to shell.

this script must run on startup. (like somethng in .profile)
i dont know how to run script @startup.

please can anyone help.
i am using solaris unix. (bash)

Is this script to display the login screen on the *console* of a Solaris box? Or for a remote connection session? I ask that because normally, Solaris console boots into a GUI -- you can't just display a menu like that.

are you looking something like this..

Code:

cat<<HERE
********************************************
1.user1
2.user2
3.user3
4.return to shell
********************************************
HERE
print "ENTER UR CHOICE==>\c"
read ch;
case $ch in
1) sudo su - user1 ;;
2) sudo su - user2 ;;
3) sudo su - user3 ;;
4) break ;;
*) print "";
   print "INVALID OPTION SELECTED " ;
   print "";;
esac

Thanks,
i also did the same thing.
Do you have any idea? can it be done without SUDO ?