Unable to find Phone Number for Validation in create/Edit contact page in Benefit VBS

Summary:

Navigation : Benefit Administrator > Benefits Activity Center > Open an employee >> People to Cover > Edit Existing Contacts >> edit Relationship

We have a requirement to restrict Phone Area Code up to 3 character and Phone Number up to 7 character in edit/create contact page.

Also, we need to display a error message if character are not matching.

We able to achieve Area Code validation and error message is displaying correctly

Problem is, when we are trying to apply same validation on Phone Number, we unable to see Phone or Number field in "Validate Field Value"

Is it feasible to apply validation on Phone Number ? If yes, how we can achieve that ?