How to send webform to two different signers without initially knowing the email of the second?

I am using a form on our website that sends users to a webform with url parameters that fills out the webform with defualt values. There is logic on the website for the user to add a second user's info that also gets transferred to the web form. My question is how can I get the webform to be sent to the second signer after the first signer goes thruogh the process and signs the Adobe Web Form? Initially when making the webform I see the part where you can add other signers or approvers, however, we do not know the second signer's email address till the first signer inputs it into the website and it gets sent over with the url parameters. I thought about creating logic in the website code that could send an email to the second signer's address once the first signer submits the form on the website and gets sent to the web form url. However, we need the second signer to sign the same document that the first signer has signed so it would have to be one at a time. Is there any workaround for this on Adobe Sign. We have used Docusign and you can easily do this with powerforms, but I do not know how to implement this with Adobe Sign. Any help would be greatly appreciated! Thank you!