Hi John,
I found the solution to this problem by using php function ‘use’. See below.
Thanks for your help!
$select_fields = array( 'cornices', 'bedrooms-flooring' );
foreach ( $select_fields as $var ) {
add_filter('acf/load_field/name='.$var.'-select', function ( $field ) use ($var) {
// some code using $var
});
}