Return specific text when the answer is not found

I have a prompt where I submit a document and the prompt asks to find a specific restriction. ChatGPT4 does a good job of finding the restrictions. However, when it does not find the restriction, I need the answer to be formatted a specific way.

These are the instructions after the document text:
Please format all answers as “Label: Answer” (e.g., SomeLabel: SomeAnswer).
Make sure you answer the questions exactly as requested.
And for cases where the answer is not found, you can specify it explicitly like this:
“SomeLabel: ‘AnswerNotFound’.”

And this is the question:

  1. Find a restriction limiting the number of pipelines on a right of way or easement. Label: NumberOfPipes

A typical answer it provides which is perfect:
NumberOfPipes: This right of way grant is limited to one (1) pipeline.

However, when it cannot find the answer, it answers like this:
NumberOfPipes: The contract does not contain a specific restriction limiting the number of pipelines on the right of way or easement.

I want it to answer like this:
NumberOfPipes: AnswerNotFound

I tried revising the prompt many ways with no luck. Can someone give me guidance on how to get the correct response when it does not find the answer?

Thank you.