Get Environment Variable

How can I get a system variable in my journaling code?
I'm not asking for the Windows System Variable like UGII_BASE_DIR. That can easily be done by something like this.

Dim baseDir As String = Environment.GetEnvironmentVariable("UGII_BASE_DIR")

I'm looking for the variables which is listed in ugii_env.dat or ugii_env_ug.dat. Like for instance UGCHECKMATE_USER_DIR