Hi Anil,
If it is possible, develop a Z program and schedule it background to get the values periodically from ECC tables and update it in a Z table. The same way, you can use the ORDER_SAVE badi to update the values in another Z table whenever a sales order is created. So whenever you run the custom report, you can use these Z tables to prepare the data.
If ORDER_SAVE badi is used, hopefully it will reduce the load in the CRM system..
Regards,
Karthi M R.