Opening files with multiple keys as program-described

Something I don't quite get, in the ILE RPG docs:

I have a file with two non-adjacent keys.
Is it possible to open this file from ILE RPG as program-described (to
avoid level-check issues without overrides, and without disabling level
checking for other programs using the file), and chain it on both keys?

How do I code this?

For argument's sake, I'll call the first key "foo"; it's 11 bytes of zoned
decimal, starting at byte position 49 in the record. I'll call the second
key "bar"; it's 9 bytes of zoned decimal, starting at byte position 39 in
the record. I'll call the intervening byte (byte position 48) "baz."

And please note that, now that I have a strictly RPG query (as opposed to
a query that was only incidentally involving an RPG program), I have put
it on the RPG list, rather than the MIDRANGE list.

--
JHHL