Regarding RESB table changes

Hi..

I m working on one interface, in which i hav RESB extraction process. For the initial run of this interface all the records should be downloaded .But on subsequent execution i need only the changed records. The problem is there is no means for me to keep track of the changes in RESB, as these are not getting reflected in change tables CDHDR and CDPOS. Also there is no CREATED/CHANGED date fields in RESB table. Does anyone know any alternative for fetching the changed or newly records from RESB table based on date?