Newbie question: different IP ranges in same reverse file?

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Hi.
Our ISP has allocated different IP address ranges to two different offices 
(say 194.131.x.x to one office and 64.191.x.x to the other).  However, 
both sites have internet facing machines that belong to the same domain 
(say johndoe.com).  All of the PTR records in the 1.1.131.194.in-addr.arpa 
file reflect only the last octet (if that is the correct terminology) of 
the IP address in the 194.131.x.x range.  However, I have one machine at 
that other site that must be referenced for purposes of the Reverse 
lookup.

Can I put an entry in the 1.1.131.194.in-addr.arpa file with the format 
(for example):

2.1.191.64     PTR   someserver.johndoe.com.

The IP address is completely different from the other addresses in the 
range, but both belong to the domain johndoe.com.  I don't think I can 
have two reverse files for the same domain.

Any guidance would be greatly appreciated.

TIA.

Russell