Generate ID on Project - Can't mark as unique field?

Hey Quick Base,

So I used the below formula in a formula field on my project table called "Project name ID"

Simple formula that is working - combine the four things below to make a unique Project Name/ID -easy

[Region Name]
&"-"
& [City]
& "-"
&[Review Date]
& "-"
& [Record ID#]

the problem is when I go to check the box to make the field "must be unique" - it gives me the attached error - how do I make the field comply with this rule? the field type is just a simple Formula text field (not rich text)

Thank you,

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Jack Woods
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