PhP file to edit, but unfamiliar with php

[FunkStar]

i want to integrate an affiliate script with a shopping cart,for that i need to edit 2 php files but the tutorial is not easy for me because i'm not familiar with php.For example : \[quote\] Open the "wp_eStore1.php" file and find the following function: function eStore_get_custom_field_value() once you find it just add the following towards the end of the function (just before the return statement):\[/quote\]\[code\]$name = 'jrox_cookie';$value = http://stackoverflow.com/questions/3736659/$_COOKIE['jrox'];$custom_field_val = append_values_to_custom_field($name,$value);\[/code\]Where should i add those 3 lines in wp_eStore1.php ?This is the source code of this file : http://pastebin.com/nwZixJZa the function is located line 676Thanks