Trying to write a Validation Rule for a Custom Field on a Custom Object to handle this scenario --- If a Lookup Field is not populated, then a Picklist field and a Text field are required to be populated --- but not prevent this scenario --- If the Lookup Field is populated, then the Picklist may be updated (but is not required), and the Text Field should not be populated.

Tried coming at it a couple different angels and can't get it right. Any thoughts?

Trying to write a Validation Rule for a Custom Field on a Custom Object to handle this scenario --- If a Lookup Field is not populated, then a Picklist field and a Text field are required to be populated --- but not prevent this scenario --- If the Lookup Field is populated, then the Picklist may be updated (but is not required), and the Text Field should not be populated.

Tried coming at it a couple different angels and can't get it right. Any thoughts?