[kinook]

If 'Tools | Application Options | General | Include environment variables in system macros' is checked, you can use

Application.Macros(vbldMacroSystem)("ENV_VAR")

You can also access them directly from a script event. Here is a VBScript example:

Set shell = CreateObject("WScript.Shell")
Builder.LogMessage shell.ExpandEnvironmentStrings("%PATH%")