If when you say

open our existing records in the portal

you mean the form widget, as far as I know it does not support formatters. Formatters being the "standard" way of adding variables to forms in Platform UI.

If you don't mean the form widget, you need to provide more information as to what exactly displays those records.

But either way, if we are talking portal, it is not possible without heavily modifying the form widget or by developing a custom widget that does it.