In-cell drop down list, show from one list but output from another?

Basically I'm asking if it's possible for a in-cell data validation list drop down to show me the contents from one list, but when I click it, it outputs from another.

The context is that, the user needs to type the product's code in, and it will VLOOKUP it's description/name, but in the code column, there would be a in-cell dropdown containing the description of the products but would output its code instead, incase the user forgets the code for a product.

Or if anyone can give me another way to solve the "I need to make fast invoices one after another but can't remember all product codes"

Sorry if this is a vague post, hope someone can help me.

Here is what I have so far : https://www.dropbox.com/s/wqj9fp5p1o...oice.xlsm?dl=0

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