Hi,
Follow below steps to get your desired scenario,
1. Double click on third text box, "Text box properties" wizard opened.
2. Copy below formula to "default value" box .
concat(substring(surname, 1, 6), substring(firstname, 1, 1)).
3. Click "ok" button.
This will work for you,
K.Ramana Reddy / http://www.ggktech.comIndia.