Problems importing related data

Problems importing related data

I have an employees form (167 records) that includes a sub form to position history (330 records). The forms work properly when I manually add test data through creator. But I can not get the data to relate on import from excel.
 
I've tried uploading both forms separately, and I've tried combining excel files then selecting the option to upload sub form data on creator import. Uploading separately populates the forms correctly, but the data is not related. Uploading a combined file creates 497 records in each form.

 

This should be pretty easy, I'm probably just missing something simple.