The NVL2 has appeared in the 9i documentation, but interestingly you can get this function in virtually any 8.x version of Oracle. NVL2 is an extension of NVL, being
NVL2(a,b,c) = if 'a' is not null then return 'b' else return 'c'
and you'll probably find its available in your current release...
SQL> select nvl2(1,2,3) from dual;
NVL2(1,2,3)
-----------
2
SQL> select * from v$version;
BANNER
----------------------------------------------------------------
Oracle8 Enterprise Edition Release 8.0.6.2.0 - Production
PL/SQL Release 8.0.6.2.0 - Production
CORE Version 4.0.6.0.0 - Production
TNS for Solaris: Version 8.0.6.2.0 - Production
NLSRTL Version 3.3.3.0.0 - Production