Bulk Import to Numeric Reference Field?

Is there ANY way to bulk import data into a numeric reference field? I have 4,000 activities that I have to "assign" to their respective engagements (which have numeric identifiers) which then populates the name of the engagement in a text lookup field. The relationship is conditional to slim down the list of our engagements to only relate to the relevant contact and account. I've removed the condition for now so that I can bulk edit this field. However, it looks like the only way I can do anything in "bulk" is to first select the numeric identifier in the cell in grid edit and then fill down through the relevant activities. But, this is going to take me foreeeeeverrrrrr.  Any insight or trick would be much appreciated! Thank you!

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Cecilia Mullan
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