Can I include the NETTV key in a macro on my Universal remote control?

Only if it is a picked function, not if you have programmed a real-time macro on it.

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URC7955, URC7115, URC7125, URC7145: What is the difference between a regular Macro and a real time Macro?
URC7955, URC7115, URC7125, URC7145: What is the NETTV key for?