[Windows Environment Variables] Change user variables using VBA

Hey guys,

Do you know any possible way to modify the windows environment variables? What changes should be needed?
- To add variable with a value
- To search in the value of a variable for data, if not present to add to the end of the line

I know that VBA can use variables in order to be easy to detect some locations like : Environ("userdomain") & "\" & Environ("username") etc etc, but i don't know of any possibility of editing

Note : added picture with the location of the Windows Environment Variables