How to: Use the Values of Parent Variables in a Child Package

How to: Use the Values of Parent Variables in a Child Package
reference from MSDN: http://technet.microsoft.com/en-us/library/ms345179.aspx

To add a parent package configuration to a child package
1. If it is not already open, open the child package in Business Intelligence Development Studio.
2. Click anywhere on the design surface of the Control Flow tab.
3. On the SSIS menu, click Package Configurations.
4. In the Package Configuration Organizer dialog box, select Enable package configuration, and then click Add.
5. On the welcome page of the Package Configuration Wizard, click Next.
6. On the Select Configuration Type page, in the Configuration type list, select Parent package variable and do one of the following:
Select Specify configuration settings directly, and then in the Parent variable box, provide the name of the variable in the parent package to use in the configuration.
Important:
Variable names are case sensitive.
Select or Configuration location is stored in an environment variable, and then in the Environment variable list, select the environmentvariable that contains the name of the variable.
7. Click Next.
8. On the Select Target Property page, expand the Variable node, and expand the Properties node of the variable to configure, and then click the property to be set by the configuration.
9. Click Next.
10. On the Completing the Wizard page, optionally, modify the default name of the configuration and review the configuration information.
11. Click Finish to complete the wizard and return to the Package Configuration Organizer dialog box.
12. In the Package Configuration Organizer dialog box, the Configuration box lists the new configuration.
13. Click Close.