Help with Lookup please

[Martina_Hawkins]

I have a table called Orders. Two columns in the table are Product Code and Material Description.
I also have a table called Products with columns Product Code and Material Description (the Lookup table).
I have a drop down set up for the Product Code in Orders that works ok.
I want to lookup the chosen Product Code in the table Products to fill in the Material Description automatically into the Orders table.
I have tried
LOOKUP([_THISROW]. “Product Code”,“Products”,“Product Code”, “Material Description”)

LOOKUP([Product Code],“Products”,“Product Code”,“Material Description”)

But neither work. Any ideas on what I am doing wrong?