add a custom field in the booking form

Hello. I’m reposting my question in this new thread in case someone missed it.

I’ve managed to add another field “rprice” (reduced ticket price) successfully. What I really need now is to add another one “rspaces”, so that the total price for a booking will be: spaces * price + rspaces * rprice. I didn’t mess with the field ticket_spaces in the em-tickets table in the db, because I want it to be the total sum for regular spaces plus reduced spaces. I’ve tried several changes but I haven’t figured out the correct solution (the total price is incorrect because the code doesn’t see my custom variable). To be more specific:
in the em-ticket-booking.php

function get_price( $force_refresh=false, $format = false, $add_tax = 'x' ){
		if( $force_refresh || $this->ticket_booking_price == 0 ||$add_tax !== 'x' || get_option('dbem_bookings_tax_auto_add') ){
			//get the ticket, calculate price on spaces
			$this->ticket_booking_price = round($this->get_ticket()->get_price(false, $add_tax) * $this->ticket_booking_spaces, 2)+round($this->get_ticket()->get_rprice(false, $add_tax) * $this->ticket_booking_rspaces, 2);

The ticket_booking_rspaces variable is zero and the total price is wrong.
Can anyone please help me with this, I would really appreciate a reply, because I’m doing my thesis and I need help immediately.

http://wordpress.org/extend/plugins/events-manager/