Asus RT-N12: Repeater setup different subnet. Possible?

Hello,
I've got a Asus RT-N12 Wireless router and I can get it to be a repeater just fine. Is there a way to make the repeater use a different ip subnet. For example in part of my office they use XXX.XXX.1.5 but I'd like my repeater to be setup to extend the wireless network and use an ip from the primary router and have the RT-N12 hand out its own ip's like XXX.XXX.6.1 in a different part of the office.

Can this be setup using the latest Asus original firmware??

Thanks, ED

P.S. Did this with DD-WRT installed but do not want to use that.

Possibly but I believe you may have to fiddle with the sub-net mask. You would be better just buying a cheap wireless router, hook it up to the repeater via a Ethernet cable, and configure it to use a different address structure.