Another AS No.

Hello all, We are ISP and local-ir too, and we have 4 links (bgp) to other ISP. We are thinking about dividing our network in two AS. Reason for that is to divide network and customers so we could announce AS-es different to different bgp peers. I know that we can use route-map in bgp to announce different IP addreses, but it seems simpliest with two different AS No. So my question is : Is it possible to ask another AS Number from RIPE within existing IP space or with new IP addresses allocation? I did not find anything about another AS in ripe documents. Maybe this is stupid idea, maybe not I do not know, so I would appreciate any suggestion or advice. Thanks in advance, Anela Lovric HiNet