amrit42087 on "[Plugin: Contact Form 7] Pass a value to paypal before the form submission"

Hi I am trying to calculate a value in the function.php by calling a hook.I am using contact form 7 as a plugin. After the calculation I want that value to be passed to the paypal as an amount.

This is the function I am using in the function.php

add_action('wpcf7_before_send_mail', 'CF7_pre_send');

function CF7_pre_send($cf7) {

    //$first_field = $_POST['your-name'];
    $from = $_POST['city1'];
    $to = $_POST['city2'];

    $from = urlencode($from);
    $to = urlencode($to);

    $data = file_get_contents("http://maps.googleapis.com/maps/api/distancematrix/json?origins=$from&destinations=$to&language=en-EN&sensor=false");
    $data = json_decode($data);

    $time = 0;

    $distance = 0;

    foreach($data->rows[0]->elements as $road) {
    $time += $road->duration->value;
    $distance += $road->distance->value;
    $distance  = $distance/1000;
    $value = $distance*12;

}

After that I want to pass this $value into the paypal as an amount. I am using the following link in my sent success message for redirecting to paypal.

<div id="confirm"> <h2>Please verify order confirmation and proceed</h2> <a href="https://www.paypal.com/cgi-bin/webscr?business=xyz@gmail.com&cmd=_xclick&currency_code=USD&amount=[payment-amount]&item_name=[project]" class="submit">Continue to Payment</a> <a href="javascript:fadeIn('hideme');" class="edit">Edit / Undo / Redo</a></div>

https://wordpress.org/plugins/contact-form-7/