Hi @sordine18 ,
Welcome to Airtable Community !
You cannot do that in Airtable forms, because the record hasn’t been created it basically. You can however do that in something like MiniExtensions.com
@sordine18
No, you can only make fields that are required. There is no other validation that can be done.
Although you can conditionally hide & show fields, so you can get creative by showing your required fields under certain circumstances only.
Your best bet would be to use advanced form software like JotForm, which gives you a nearly-unlimited ability to create your own validations.
JotForm also integrates with Airtable, both natively & through automation tools like Make.