Unattended Net-install Ubuntu over Wifi with user-supplied network info

Is there a way to change the Ubuntu Ubiquity installation to not continue without an internet connection?

I have created a preseed file that automated the entire installation process including assigning the wep key using the string

d-i netcfg/wireless_wep <wep_key>

The problem i am facing is i would like the installation to stop at the "Select a Wireless Network" screen if the autmoatically configured network connection doesn't work, instead of trying to continue with the installation. Also, how do you remove the "I don't want to connect to a wifi network right now" option seen below?

(Image is from the website http://www.ubuntu.com/download/desktop/install-desktop-latest)

I have tried the Ubuntu Customization Kit but im not finding where i can have this level of control.

To do this you would need to manually edit the ubiquity installer scripts.

These are located in /usr/lib/ubiquity, and are typically owned by the ubiquity package, so if you intend to customize them you will probably want to roll your own variant of that package.

I believe the one you want to edit is /usr/lib/ubiquity/netcfg/netcfg which is actually a compiled binary, so you will need to download the Ubiquity source package to customize and rebuilt it (or replace it with something you write on your own).