I am trying to work some logic around to manipulate the grand total in a GravityForm form before it gets sent to the payment processor. I can't for the life of me figure out how to do it though. I have a calculation field that dynamically sets itself to a discount, my issue is apparently actually getting the finaltotal to recognize this amount. The code for the calculation I have right now (with the switch case omitted):

// Custom Form Logic to Change Total Base on Membership Rates
add_filter( 'gform_calculation_result', function( $result, $formula, $field, $form, $entry ) {
    // do stuff

    if ($form['id'] == 28 && $field['id']== 107){
        $membershipLevel = $_COOKIE['memberlevel'];
        $discountAmount = setFieldsPHP($membershipLevel);



        print_r($result);
        if ($result >= $discountAmount){
            $result = $result - $discountAmount;
            print_r("FINAL TOTAL: " . $result . ' WITH DISCOUNT OF: ' . $discountAmount);
        }
        else {
            $result = ($result - $result) * -1;
            print_r('<BR> FINAL TOTAL SHOULDVE BEEN: 500 - ' . $result  . ' WITH DISCOUNT OF: ' . $discountAmount);
        }
    }
    return $result;
}, 10, 5 );

Which this "works". The print_r's display the right thing upon form submission. However I seem to be missing that final step that lets me actually apply this discount to the grand total and get it to effect. Any idea what i'm missing?

Thanks!