Import requirement with custom field from Excel to RQM

Hello,

I'm using the RQM cexcel importer with no problem with this config file:
requirement.dc:title=B
requirement.dc:description=F

Now I need to import a specific field that has been inserted in the RQM project requirement schema. This is just an enumerated (technical, functional). But I failed to import it.
Do you have any idea of the line to insert in the cfg file to import such a custom field ?
I tried this and many others with no success:
requirement.externalTag.customAttributes term="RequirementType".value=C

Thanks for any help

Bernard