Possible to validate if a resource assigned has a specific skill level

I have a task that requires a specific skill and skill level and I would like to write a validation rule to check that any resource assigned has the correct skill and skill level. I got the skill part to work by checking if the link between the resource assigned and the skill exists:

isnull(GetLink('Skill name',$Resource))

Wondering how or if it is possible to check the skill level.