Get your terminology right first - CA7 is a scheduling system that submits jobs, amongst other things. Jobs consist of JCL and maybe control 'cards'.
If CA7 is like OPC (OPCA TWS whatever) then you just add the job to a Sunday only calendar. If a return code of 4 is not to be treated by CA7 as an error then you would need a separate job from your normal daily job. The Sunday job would execute an IEFBR14 as the last step or provide some other mechanism to convert your RC of 4 to an RC of 0.
The problem I have is that people can explain things quickly but I can only comprehend slowly.