Hi Dominic. There are several ways to do this. Here is one I just tested.
First, grab the free code from here:
That is PHP code that can be added to your theme functions.php file, or you can use a plugin such as this one to keep the code separate from the theme: Code Snippets – WordPress plugin | WordPress.org
Then, add a snippet like this, which will get the number of entries that exist right when the form is submitted, and store that in field 4 (in my form.)
// relies on the code from here:
// https://gravitywiz.com/shortcode-display-number-entries-submitted/
// apply to form ID 176 only
add_action( 'gform_pre_submission_176', 'how_many_entries' );
function how_many_entries( $form ) {
// where do you want to store the number of entries
$entry_count = do_shortcode('[gravityforms action="entry_count" id="176" format="decimal"]');
$_POST['input_4'] = $entry_count;
}
That code will apply to form 176 on my site, and it will store the number of entries in field 4. Field 4 is a number field with the visibility hidden on my site.
When the form is submitted, field 4 will get the number of entries that existed before that entry was created, and you can base your conditional notification and conditional confirmation message on that field.
If you have any questions, please let us know.