Button URL specific record with Everyone on the Internet

I have not totally thought this through, but what if you made a formula field of the [Record ID#] of [Related employee]  plus 98765. Call this field [Calculated Secret Code] So employee record ID #1 would have a value of 98766.

Then when you send the link populate that field on the record called say [Access code].

For that EOTI Role, make a permission that they can only see records where the [Secret Code] = [Calculated Secret Code]