Name Foreign Constraints, Append ChildEntity ColumnName

I'm trying to modify the sample macro, 'Name Foreign Constraints', to include the attribute name from the child entity in the relationship. I'm having some trouble pulling that property from the relationship. My target naming convention is: 

FK_<relation.ParentEntity.TableName>_<relation.ChildEntity.TableName>_<For a given relationship, Column Name of attribute with the FK constraint in the child entity>

Based on my understanding of the documentation I tried the following approach, which returns "Object var is 'nothing'.":

    For Each relation In mdl.Relationships
            ParTable = relation.ParentEntity.TableName
            chiTable = relation.ChildEntity.TableName
            chiattr = relation.FKColumnPairs.Item(relation.ID).ChildAttribute.ColumnName

 

I am not fluent in basic, so this may just be bad syntax. Would appreciate any pointers.