I am attempting to End Date some Recurring Element Entries and need to find the Source System ID

Summary:

We are updating a number of Element Entry's for employees with updated information. I am attempting to do so through an HDL but have been receiving the error "The effective dates on this new element entry are invalid. This entry causes an overlap with an existing entry for the same element." I believe that what I need to do is to apply an end date to the existing entry and then the new entry can be added. However, in order to add an end date I need to find the Source System Owner for the Element Entries. I have not