Add Customer IP address to invoice

-- HikaShop version -- : 2.4.0
-- Joomla version -- : 3.3.4

I am trying to add the customers IP address to the admin invoice that gets mailed to site owner. We need to have that present on the printed invoices. Is there a way to add this. what is the code. I have seen other messages about adding email addresses, but i need to add the customer ip address.

Thanks

Thank you for the response.....but can you walk me through how to do that ..step by step.

Example: The current invoices we print for our records have the following information-

SUMMARY OF THE ORDER

Customer:
Order Number

Payment Method

Shipping Method

Billing Address Shipping Address




Name Unit Price Qty Total

Subtotal
Shipping
Total

I am trying to add a field that would show :customer ip address: somewhere on this form, preferably after order number.

Thanks