Homebrew: Can you cap a modifier contribution?

I'm trying to acquire this equation for a race:

AC = 13 + Dex modifier (maximum of 2) + proficiency bonus.

How would my modifiers be setup to accomplish this?  In particular, is there a way to put a maximum limit on the dexterity modifier contribution like the equation calls for?

Looks like for AC's Dexterity modifier you can cap it as:

Set - AC Max Dex Modifier

If you need something more specific, I don't think it exists.

• Modifier: Set->Subtype: Unarmored AC->Fixed Value: 3->Additional Bonus Type: Proficiency Bonus
• Modifier: Set->Subtype: AC Max Dex Unarmored Modifier->Fixed Value:2

You would need the combination of those two modifiers.^^^