Data Replication

We are in the process of setting up a system which will consist of 19 seperate sites connected through Frame Relay. Each of these sites will have an Informix SE Database which we need to keep synchronized with all the other sites. The way we would like to synchronize the databases is, when a change is made at a remote site, update the remote database, then forward the change to the headquarters machine. At that point the headquarters machine would update the other 17 sites. The headquarters machine is connected through a T1 and the other sites are connected via 56K links. All the machine will be single Intel Pentium running SCO UnixWare 2.1. Does anyone know of a product that will synchronize SE databases? Informix indicated we need to upgrade to ODS 7.23, which is allot more expensive than I expected. Any input would be appreciated. Thanks Shannon