Pushing an item from one list box to another on button click. But how we have the items selected.

I'm wondering if the parameter would be available if you created a "supplied parameter" and referenced the parameter that is missing and placed the "supplied parameter" on the dashboard that contains the list.  I may be missing something, but it almost sounds as if the parameter is not making its way back to the dashboard.  Have to think about reasons it wouldn't have the parameter value after setting it in the BR.