Adding Users to Custom User List Automatically

I am wondering if there is any way when I add a user to one of my apps, that if that user is in a certain role, that they can be added automatically to a user field that has a custom user list?

Or can a user field with a custom user list pull based on the user role?

This would save me a headache since I tend to forget to add them to the user fields.

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Carol Mcconnell
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