sum_list_column.php

<?php
add_filter( 'gform_calculation_formula', 'sum_list_column', 10, 4 );
function sum_list_column( $formula, $field, $form, $lead ) {
    // {List:1.3} - {Label:ID.Column}
    preg_match_all( '/{[^{]*?:(\d+?).(\d+?)}/mi', $formula, $matches, PREG_SET_ORDER );

    if( is_array( $matches ) ) {

        foreach( $matches as $match ) {

            foreach( $form['fields'] as $field ) {

                if( $field['type'] != 'list' && $field['id'] != $match[1] )
                    continue;

                $list_values = unserialize( $lead[$match[1]] );
                $column = $field['choices'][$match[2]-1]['text'];
                $sum = 0;

                foreach( $list_values as $value ) {
                    $sum += GFCommon::to_number( $value[$column] );
                }

                $formula = str_replace( $match[0], $sum, $formula );

            }

        }

    }

    return $formula;

}

Hi richardW8k,

Thanks for this. Is there any way to modify so that the sum appears in real-time, as users enter data in list fields? I know that the 'gform_calculation_formula' filter only works when a user submits, but is there any other way to get the same result, except in real-time?

Thanks