This actually came up during our live GoldMine presentation at Villanova university.
If you create a new userdefined field and use the word "PHONE" in the FIELDNAME, the field will automatically format any inputted phone numbers.
1. Create a new userdefined field called PHONE4
2. Rebuild your database
3. Now, entering 5556667777 into the PHONE4 field results in (555)666-7777
Pro Tip : Always omit the first "1" in a long distance number in GoldMine, else it won't format it correctly.