Maintain the context in an RFC_Lookup reponse

I have a multi-row input message which is mapped into a multiple IDocs.

I have a Z RFC function which is called during mapping each time with the relveant value of the context.

In the RFC Looukup response I might get values + context change between them

but some times I can get null values (not empty context) with no context change.

How can I maintain the context of the reponse so it can later be split to each target mesage.