Assigning Lync / Skype telephone numbers

Hi,
I'm setting up a template to create our AD accounts and want to user it to create enterprise voice Lync/Skype accounts. On the OCS/Lync/skype tab there is a "Line URI format" box where I've entered tel:+<externalnumber>;ext=%telephoneNumber%, with AD Manager picking the telephone number up from the General tab.

1) When i log in as a technician the telephone number field is greyed out, can i change it so numbers can be entered?
2) Is it possible to auto fill this field from a text file.

Assigning numbers seems a unnecessary manual task, you'd think there would be a way of Lync picking an unassigned number and using it.

Thanks in advance
Darryl