How to manipulate data while inserting data staging into target table using Data entities D365

Hi

I’m having a requirement, Need to create new data entity.

While import process ,data inserting staging to target table I need to write custom logic like based on customer account, cust group need to fill in the target table.

I tried copyCustomStagingtoTarget method, it doesn’t help me.

Can any one help me!!!

Thanks in Advance