include in product xml?

[Dylanblitz]

I have a product xml that has an include statement to call a php file. It used to work in 3.x but with 4.x it keeps saying it can't find the file. I've tried changing it to require_once and require with no dice. Anyone know the proper syntax to call a php file located in the admincp from the install code of a product?

The line is

require_once(DIR . '/admincp/garage_update_2.0.0.php');