Custom ConfigurationSection to external .config

I know there is an easy way to move any "standard" config section to external file i.e.

<appSettings file="myFile.config">

but what about a custom ConfigurationSection?

<configSections><section name="someName" type="Namespace.SomeNameConfiguration" requirePermission="false" /></configSections>....<someName>< bla bla bla ......</someName>

Is there any similar way?