IAM Policy to allow update on a deeply nested attribute in DynamoDB

Question

This article talks about fine-grained column and row level access control with DynamoDB.

However, what if I want to allow a user to UPDATE only a deeply nested attribute inside a column of DynamoDB ?

For eg: I have this object stored in DynamoDB:

{
  "Id": "123",
  "Parent_Prop_1": {
    "child_prop_1": {
      "sub_child_prop_1": "some value"
    }
  },
  "Parent_Prop_2": {
    "child_prop_1": {
      "sub_child_prop_1": "other value"
    }
  }
}

Is it possible to write a policy that allows a certain user to only perform update on this path: Parent_Prop_1.child_prop_1.sub_child_prop_1 and no other paths ?