Civi membership receipt emails - how to turn on/off per membership?
Membership online receipts are delivered based on which Contribution Page someone completes. So if you used multiple such pages, you could turn off 'send receipt' for some of them.

If they all have to come in from the same page for some reason then alternatively you may be able to run a post-process hook and change the the civicrm_contribution.contribution_page_id value, or since this is memberships, it may relate to the value in civicrm_membership_block.entity_id value (guessing a bit here but the membership block is set to be on specific contribution pages by this value, and that may therefore link to the Contribution page ID and hence whether a receipt gets sent or not)