You can use a query to get records you want into a cursor first and than add them to the Group table.

SELECT * FROM master ;
  WHERE code NOT IN ( SELECT code from Group) ;
  INTO CURSOR crsTemp
SELECT Group 
APPEND FROM ( DBF("crsTemp") )
USE IN crsTemp

In VFP8 you can do that in one step using INSERT INTO SELECT FROM command.

>
>I have two tables the first is "Master" and the other is "Group".
>The both tables has common fields as
>
>code n(6)
>name c(40)
>
>For Group table, I want to copy, from Master table, only those codes that are not exists in Group table.
>
>Index is on code field.
>