How do I point my app.config appSettings' external file to point to a path using an environment variable? The below is not recognized:

```
<appSettings file="%AppData%\MyApp\MySettingsFile.config" />

```

However, absolute paths are recognized, even though they are not within the hierarchy of the output path of the assembly, such as:

```
<appSettings file="C:\MyApp\MySettingsFile.config" />

```