Hi @Pets52Dave,
Thank you for your question in the Klaviyo community!
As @kaila.lawrence mentioned, this isn’t available natively in Klaviyo, but there might be a possible work around here.
If your paid membership is based on a custom profile property in Klaviyo you could actually sync this back into Shopify’s customer Metafields. Instructions on how this works here.
You could already validate the access to the page with the form based on the customer metafield in Shopify by using liquid. This look something like this:
{% if customer.metafields.klaviyo.Paid_member == "Yes" %}
<p>Welcome paid member. See your signup form below</p>
{% else %}
<p>You are not yet a paid member. Sign up below!</p>
{% endif %}
I hope that helps. If you are wanting to serve up the form either way, you could always duplicate the form so that you are able to differentiate between paid and non-paid members.
I hope that helps!
Thanks
David