From USER A:
------------
usera>>cat file1
#!/bin/ksh
file2

usera>>cat file2
#!/bin/ksh
echo this is file2

usera>>chmod 755 file1
usera>>chmod u+s file1 
usera>>chmod g+s file1
usera>>chmod 700 file2
usera>>ll file*       
-rwsr-sr-x   1 usera    useragrp         27 Apr 25 16:12 file1
-rwx------   1 usera    useragrp         30 Apr 25 16:05 file2

files:
total 0

## file1 runs file2 OK from owner
usera>>file1
this is file2


From USER B:
------------
## also fine from other user
userb>>file1
this is file2
## but other user can't exec file2 directly
userb>>file2
ksh: file2: cannot execute