Multiple Record Insert

I am trying to do an update to a database with the code below, the code will work in generating a single record (if i exclude the IF statement) but i need it to create multiple new records based on the IF statement (or something similar) i have in the code. It needs to create updates for every record that has a parentguid that matches the one specified in the code.
the idea is, the hierachy structure in the tables are:

Location1
--> Part1
--> part2 etc
Location2
--> part1 etc

i want it so that when i input a new part it updates to all the locations. The locations all have the same parentguid (the one specified in the code)
With regards to the stored procedure it executes, this stored procedure creates the entry. I don't really want to change the stored procedure because other functions reference and use it.

My code:

DECLARE @PREFIX VARCHAR(6)
DECLARE @CODE VARCHAR(8)
DECLARE @GUID UNIQUEIDENTIFIER
DECLARE @PARENTGUID UNIQUEIDENTIFIER
DECLARE @PARENTGUID2 VARCHAR(50)
select @parentguid2 = parentguid from dsdba.itemgroups

if @PARENTGUID2 = '8CF850AD-2026-411B-AABE-BF1584624EB3'
BEGIN

SET @PREFIX = 'JUST'

SELECT @PARENTGUID = GUID FROM DSDBA.iTEMGROUPS WHERE CODE = @PREFIX

SET @CODE = @PREFIX + '02'
SELECT @GUID = NEWID()

EXEC DSDBA.usp_ItemsDB_InsertGroup @GUID, @CODE, 'JMB', @PARENTGUID, 1

END

:confused: