Using a formula within Zapier to update Airtable field?

I have a zap that I would like to take an existing date from a field in AT, add a constant amount of time to it, and then insert the result as the value for a different field on the same record.

For example, if record A had “Creation Date = 11/15/2021” I would want my formula to add a constant of 30 days, then insert the result (12/15/2021) into the previously empty “Due Date” field for the same record.

I know Zapier has support for formulas in it’s “Search for Records” step, but I don’t see any of those capabilities in the 'Update Record" step. Does anybody have any experience with this, or know where I could find documentation?

For anybody else in a similar situation, I ended up solving this by creating a google calendar event within the same automation and then updating the record again using the date from the google calendar event, which I can set whenever I want using date arithmetic. Suffices for the time being with no need to create helper fields!