Local Peering and Transit - BGP multihoming

Dear all, In my lab, i manage two ASN (100,200). ASN100 has one transit to ASN300 and local peering to ASN500. ASN200 has one transit to ASN400. ASN100 do private peering to ASN200. Some policies are required as below: 1. ASN100 customer can only use ASN300 for transit 2. ASN200 customer can only use ASN400 for transit. 3. Local traffic will stay local between ASN100,ASN200 and ASN500. 4. ASN100 and ASN200 are backup each other only if either upstreams is down. How to configure BGP to meet the above policies? I am using Cisco devise. best regards, chanty