Using the same equation for several inputs

Like, a real worksheet or a proof of concept?

I assume you're referring to the "Inputs for functions and programs. Often when performing calculations, we want to limit inputs for functions and programs to pre-defined values, which subsequent users of the worksheet may be unaware of. For example, engines may be available in specific settings for volumetric displacement, number of cylinders, or speed (revolutions per minute). Financial worksheets might have a limited number of interest rates or periods." from the blog article.

If you're fine with a proof of concept that I just made up right now, it might look something like the attached. Pretend what's in the protected area is some very important program and/or function that you don't want your readers to mess with, and the values of the combo boxes are important to your mission. You can use the combo boxes, which have those preset values you've set up, as a configuration management tool at that point.

That's actually what real Mathcad customers do, now that I think about it, like Haley Barnes from SRAM. (That links to a case study presentation.) She uses Mathcad "template models" with dimension inputs / dimension outputs (she connects it to PTC Creo, a 3D CAD program) for bike forks/crowns. She doesn't quite show the programs / functions to the audience because I'm pretty sure they're hidden in the collapsible areas, and I don't have her worksheet because of it being highly proprietary, but she does use the combo box values to change dimensions on her model and she does some kind of checks with those values within Mathcad to make sure they're within specification.