On each form submission I am saving an array in meta, and on form completion I am trying to update the meta. But since it's a multidimensional array I am trying to target only the current matching array to update "inactive" to "active". And a form completion might not be the last or current array. It could be completed at a later time.

gistfile1.php

<?php

function submit_form() {
    $value = array(
    	'key'		=> '', // Array key?
    	'date'		=> date( get_option( 'date_format' ) . ' ' . get_option('time_format'), current_time( 'timestamp', 0 ) ),
    	'name'		=> $user_name,
    	'email'		=> $email,
    	'hash'		=> $hash,
    	'message'	=> esc_textarea( $_POST['commentText'] ),
    	'activated'	=> 'inactive',
    );
    add_post_meta( $post_id, '_my_custom_meta', $value, false );
}

function complete_submit_form() {
    $post_meta = get_post_meta( $post_id, '_my_custom_meta', false );
    
    //Prob need a foreach loop and find some key to update just the [activated] key
    update_post_meta( $post_id, '_my_custom_meta', 'active', $post_meta[$key]['activated'] ); //??
}

/**
 * Post Meta array output:
Array
(
    [0] => Array
        (
            [date] => March 12, 2013 7:20 pm
            [name] => Austy Frosty
            [email] => afrostyy@***.com
            [hash] => f577349fad301a9e5d2304404a02f86a
            [message] => Yo dawg!
            [activated] => inactive
        )

    [1] => Array
        (
            [date] => March 13, 2013 12:18 pm
            [name] => Just Boots
            [email] => afrostyy@***.com
            [hash] => 75ef8e4a8a8c7cbbb6698add2054c305
            [message] => I would like to view this post.
            [activated] => inactive
        )

)
 */