CRM datasource 0CRM_SRV_PROCESS_H enhancement

Dear all,

Please advice me how to enhance datasource in CRM - it's like in R/3 or another?

There are 2 datasources 0CRM_SRV_PROCESS_H and 0CRM_SRV_PROCESS_I and field WARRANTY is available only in 0CRM_SRV_PROCESS_I

I'd like to add to 0CRM_SRV_PROCESS_H field ZZWARRANTY and get data from table CRMD_SERVICE_I based on CRM Order GUID

What is the best way to enhance datasource in CRM?