How to Reverse Scrollwheel in Adobe Illustrator (holding Alt) using Karabiner?
Use Option::KEYTOKEY_BEFORE_KEYDOWN together with KeyCode::VK_CONFIG_:

&lt;?xml version="1.0"?&gt;
&lt;root&gt;
  &lt;item&gt;
    &lt;name&gt;invertscrolling&lt;/name&gt;
    &lt;identifier vk_config="true"&gt;invertscrolling&lt;/identifier&gt;
    &lt;autogen&gt;__FlipScrollWheel__ Option::FLIPSCROLLWHEEL_VERTICAL&lt;/autogen&gt;
  &lt;/item&gt;
  &lt;item&gt;
    &lt;name&gt;test&lt;/name&gt;
    &lt;identifier&gt;test&lt;/identifier&gt;
    &lt;only&gt;ILLUSTRATOR&lt;/only&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::OPTION_L, KeyCode::OPTION_L,
    Option::KEYTOKEY_BEFORE_KEYDOWN, KeyCode::VK_CONFIG_TOGGLE_invertscrolling,
    Option::KEYTOKEY_AFTER_KEYUP, KeyCode::VK_CONFIG_TOGGLE_invertscrolling&lt;/autogen&gt;
    &lt;autogen&gt;__KeyToKey__ KeyCode::OPTION_L, KeyCode::OPTION_L,
    Option::KEYTOKEY_BEFORE_KEYDOWN, KeyCode::VK_CONFIG_TOGGLE_invertscrolling,
    Option::KEYTOKEY_AFTER_KEYUP, KeyCode::VK_CONFIG_TOGGLE_invertscrolling&lt;/autogen&gt;
  &lt;/item&gt;
&lt;/root&gt;


More information about KeyRemap4MacBook:

http://pqrs.org/macosx/keyremap4macbook/xml.html.en
https://raw.github.com/tekezo/KeyRemap4MacBook/master/Tests/lib/string/data/checkbox.xml
http://osxnotes.net/keyremap4macbook.html