extending out dates

Hello

I have a csv file where some of the data needs extending based on what is in current file.
Sample data as follows.........

Cpy                         Period         Repeats       Date                    Value
A001-20110130       Monthly          3              01/02/2011         100
A001-20110330       Null                0              01/04/2010           45
A004-20110130       Quarterley      2              10/02/2011         234
A005-20110130       Null                0              01/06/2011         100
etc
so, based on above data I need to add rows based on "Period & Repeats" columns having values.
Row1 will now have 3 more rows added and the only thing that will change is the date column.
Row 3 will have 2 more rows added and again only the date value will change. The idea is to extend out the dates based on columns "Period & Repeats." Now, my new data set based on the above rules should read as follows....

Cpy                         Period         Repeats       Date                    Value
A001-20110130       Monthly          3              01/02/2011         100
A001-20110130       Monthly                          01/03/2011         100
A001-20110130       Monthly                          01/04/2011         100
A001-20110130       Monthly                          01/05/2011         100
A001-20110330       Null                0              01/04/2010           45
A004-20110130       Quarterley      2              10/02/2011         234
A004-20110130       Quarterley                      10/05/2011         234
A004-20110130       Quarterley                      10/08/2011         234
A005-20110130       Null                0              01/06/2011         100

Hope this makes sense.

Regards