Nest, Locking high + low temperature

[Diana Mulvihill]

Hi All ~ Me again, you have all been such a great resource (thank you!) that I think likely you can outdo Google customer service, haha. I have heard people on these forums talk about using the Nest thermostat to set a maximum low + high temperature, to keep guests from blasting the a/c or accidentally bumping the heat up to 98. 

I couldn't figure out how to set it, called Google support, they can't either. How do you set this function: I would like guests to be able to manually control the heat/ac, but would like the range of temperatures allowed be between 68 + 78 degrees.