Automate User Table Updates Based on Existing Company Rows

Request: Write to Other Table, but only a column(s) when rows already exist, meaning:

I want to send an HTTP request from the Companies Table to the backend to create the company and once the ID has been retrieved I want to trigger a Write to Other Table where it writes the actual database ID for the already existing users and then once that ID has been populated int he users table, execute an HTTP request to create the Users in the database. All can be done automatically with Auto Update and Run If, except for the part of only writing a specific column in another table when the other table already has rows.