How to detect similar name sin two columns?


I have two columns in my app, both of the type “Name”. I do not want similar names in both the columns, for this is used the function NOT(IN([C1],[C2])), and is working fine. But the issue I am facing is, for example, if I input the name ‘Peter’ in C1 and name ‘Peter Parker’ in C2, it should throw an error but it is not. Kindly let me know, how can I do this?

Though I don’t understand the intent, but for that specific case, you might need to use CONTAINS.