Automatically assigning based on form submission

Assuming the Certificates table is named "Certificates"...

Create a linked record field on the Recipients table that links to Certificates. On each table, the name of the field should be the name of the other table.

Create an Automation with the following configuration:

Trigger: When a form is submitted

• Table: Recipients
• Form: *YOUR FORM NAME*

Actions

Find Records

• Table: Certificates
• Find Records Based on: Condition
• Conditions: Where Recipients is empty
• Maximum Record Limit: 1

Update Record

• Table: Recipients
• Record ID: Airtable Record ID from the "When a form is submitted" step
• Fields:
  • Certificates: List of 'Airtable record ID' from the "Find Records" step

In layman's terms, here how the automation works:

When a form is submitted, look for a record in the Certificates table that is not currently linked to a record in the Recipients table. Then, update the record in the Recipients table to link to the record from the Certificates table you found earlier.

Note: This will not select the "next" open certificate number, it will pick one at random. If you need it to follow a certain order let me know.

Hello @Sean_Lake1,
I expect that you've also asked for the certificate number as a field in the first form(Recipients).

At the moment Airtable doesn't support trigger action in the middle form filling or multiple steps to handle form data.

So I recommend you to use Fillout Forms which has inbuilt native integration with Airtable. It also supports multiple steps and subforms which is useful for your implementation.

Use multiple or subforms then add a record to Airtable when the first part of the form is complete. Trigger Airtable automation to link certificates based on number. Then based on the first submission show the linked certificate on the second form step.

If you've already used Airtable Automation then implementation of the Fillout form will be easy for you.

I hope this helps you.
Let me know for further enhancement of suggestions. 
👍

Yeah, sadly we cannot access external software without a long period of approval through legal, etc.  

@Sean_Lake1 did the solution I provided above work out for you?