Export data from an entity for reimport in another entity

Hi all,

I need to use the content of an export of entity X, in order to update entity Y by reimport.

X and Y have a 1:N relationship.

This is what I am doing :

1) Export records from a view from entity X. This view displays a lot of fields from entity Y, including the GUID.

2) Replace primary keys (column A of the export) of entity X by the GUIDs of entity Y. The goal here is to modify the Excel export to make it look like it was initially exported from entity Y.

3) Submit file for reimport

What is wrong is that CRM still thinks the file contains records of entity X. The import wizard doesn't even ask me what entity I am trying to import and automatically assumes it is entity X. Of course all lines fail, because I tampered with the primary keys.

Do you know how I could make CRM forget that my reimport file originally came from entity X and make it accept my file as containing records from entity Y ?

Is there another way I could achieve this ?

Thanks