Hiding the debugger from a third party executable

I have a DLL written in Visual C ++ that runs with a third party program (via a standardized interface) and I need to know if it does my function correctly, if at all.

Usually I can just select the executable as the debug input command, but that particular executable might somehow detect that the debugger is connected and refuses to work.

It displays the following message:

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PRISM 8.1.1
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Debugger found

A debugger was started on your system.

Please unload it from memory and restart your program!

Please visit: www.prism-astro.com for support.
---------------------------
OK
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How to hide the debugger from the program. Please note that I am only trying to debug my DLL, not a third party program, so I don't think there should be legal problems.