I have a form (form A) with a repeater field for email addresses that, upon submission, creates a post and adds those emails to an ACF repeater custom field. I have another form (form B) that I want to use to capture additional email addresses and add them as entries in form A's repeater.

The reason I'm doing this is that I want the second form to send an email to those emails upon submission. Think of it like inviting a person to that post. Form B lives on the newly created post, so I'm thinking I could use the current post meta data to determine which form entry is tied to it, but not sure if that's possible.

Ideally I'd do this with one form, but I don't want to send emails to every email in the repeater each time, just newly added emails, and I'm having trouble accessing the array for the repeater to compare to the array in the custom field.

Any idea how this can be achieved? Thanks!