dotNet API PROCESSCMD

Sage 300 dotNet API project. Lots of the available docs say to use create a macro in the UI for what you want to do and then translate to C#. Works great for most of it but I am having an issue with the PROCESSCMD lines, which are often necessary to get optional fields that are set to automatically populate to actually have that happen.
Macro line is
ARCUSTOMER3headerFields("PROCESSCMD").PutWithoutVerification ("0")

C# translation is
ARCUSTOMER3headerFields("PROCESSCMD").PutWithoutVerification("0");
but Visual studio says: "Error CS1955 Non-invocable member 'ARCUSTOMER3headerFields' cannot be used like a method."

Anyone know how to work around this?