Using a variable in the code is not working the same as putting in the exact webpage

I have an input file that holds all the data I need for my tests.  This allows the user to update as needed and still be able to run the tests.  I also want to be able to use this file to select the environment to run the tests.  Since it is a webpage, I figured I could just replace the address with the variable and it would work the same.  I am not finding this to be the case.  The first problem I am running into is that it isn't recognizing the .Wait functionality that I absolutely need.

These fail

var testenvironment = getTestCase("environment").Entered;
testenvironment = "Aliases.browser." + testenvironment;

testenvironment.Wait(10000);

var testenvironment = getTestCase("environment").Entered;

Aliases.browser.testenvironment.Wait(10000);

But this works

Aliases.browser.NameMappedWebPageCom.Wait(10000);

I don't understand why it fails.  If I can't get this simple statement to work, I don't want to waste my time changing all of my scripts, but being able to just feed in the environment would be fantastic

Thanks