Crystal report - Create filter as query

Hi Experts,

I have a scenario where I need to build report on two data sources - Oracle and SAP ECC function module.

First i need to fetch a Customer number from oracle database based on some selection and for only those customer ECC function module should run and get details of customers.

As of now I have created a join between these two table in Database Expert. But it it taking too much of time to get data as record by record it is executing ECC function module.

Can I first select customer from oracle and pass these customer as a filter to ECC function module, i.e. create a filter  on Customer of ECC function module which will get data through a query . Is it possible?

Thanks in advance.

Regards

Rakesh