matching field on import?

[#1]

I have 250 new customers (and many more existing) and I'm trying to import a table of referenceIDs matching my existing Square customers. This is where I'm getting stuck:

I have created a CSV file that is the Square Customer ID and the ReferenceID from my database of customers. I want to import them into Square and use Square's Customer ID as the match field so the ReferenceID is populating the existing customer records at Square. IS THIS POSSIBLE or will all imported items be new records?

[#2]

@MacITArk ;

This sounds like it should be possible.   I know when I update or make Changes for my Items, Square uses the Column Token as the field that can not be changed by users and if Blank then it makes a New Item.   I do not have any experience adding Customers by CSV, and which Column would be the one that would be Left Blank for a New Customer.  

I would only be Guessing that the " Square Customer ID" would be similar to the Token field in the Catalog CSV file.  You would need to ask someone at Square like Square Moderator like @Violet_  might be able to either answer your question or point you to someone that can.