pmpro_content_message

Here is the code in the content filter function that displays this text. You can use something similar:

https://github.com/strangerstudios/paid-memberships-pro/blob/dev/includes/content.php#L271-L288

thanks for your help

This message is displayed twice if I have the excerpt and the content on the same page. Is there a way to only display it once and not multiple times?

cheers

That depends on how your theme and templates are set up, but you you could check for membership first with pmpro_hasMembershipLevel() and then choose to display either the content or excerpt.