Here is the next in my series of posts explaining how common tasks in DTS can now be implemented in SSIS.
Passing a parameter from a parent package to a child package
In DTS, packages could execute other packages by use of the Execute Package Task. Values could be passed between these packages using the Inner Variables and Outer Variables tab of the Execute Package Task.
In SSIS, a package can also execute other packages just as one could in DTS. Inner/Outer variables have disappeared and in their place we have parent package configurations. These allow us the capability of taking any value from a calling (i.e. parent) package and setting a property in the called (child) package to have that value. That property could, and often will be, the Value property of a variable and hence we can set variables in a called package to the value of something in the calling package. Note that the altered property could be a property of any of any container in the control-flow, hence giving us much more flexibility than in DTS.
To learn more about passing variables between packages go here.