process_shipping_settings() not firing when clicking "Save Changes"

Hello,

I have created a few options using the function "shipping_settings_box()" . I would like to use the options that the admin will choose in the "extra_shipping_field()" function. Since this function does not have access to the $settings variable I thought I would use the "process_shipping_settings()" function to save the desired variables.

However, it appears that this function does not run, or at least does not run when I click the "Save Changes" button. Is this a bug? Or does this function run at a different time?

Thanks
DM