Stumped By SQL Challenge

Here is the table:

CREATE TABLE [child]
(
[pk_child_id] [int] NOT NULL ,
[fk_parent_id] [int] NOT NULL ,
[code] [char] (2)NOT NULL ,
[dt] [datetime] NOT NULL ,
[newcode] [int] NULL
)

There is a situation where there will be more than one record with the
same [fk_parent_id] value, but different values for the [code]field.
If one of those records has a [code]= 5, but the [dt] is AFTER a
similar record where [code]= 6 or [code]= 7 (but same [fk_parent_id]
value), I need to set [newcode] = 10. How can I pull this off? Again,
the group of records can have different [code] values, different [dt]
values, but a common [fk_parent_id].

Help!