We have developed a simple extension.
Name: biber Screen Name Changer
Version: 1.0.0
Compatibility: Tested only with EE 1.6.8.
Description:
The extension enables EE to create screen names on the fly based on predefined custom profile fields.
Requirements:
You must have at least one custom profile field of type “text” defined, and that field(s) must be able to be filled in by your site’s users during registration.
Example:
Let say you defined First Name (name_f) and Last Name (name_l) custom profile fields and set them to be visible in registration form.
You can go to extension settings and add name_f,name_l to field names and - to separator field.
Now, when a new user named John Doe registers to your site his screen name will be automatically created as John-Doe.
Installation:
Just unzip the package and move the file located in extension folder to your EE installation’s extension folder and move the file located in language folder to your EE installation’s language / English folder.
Then go to EE CP / Utilities / Extensions and activate the extension.
Download:
http://publicdownloads.biberltd.com/ee_extensions/ext.bbr_screenname_v1.0.0.zip
& that’s it for now! 
Can Berkol
biber Ltd.
