PostBack and value stored in dynamically created DropDownList

I have a GridView storing a dynamically created DropDownList control in one of the cells (for each row).  When I click a Button, which causes a postback, the data in the DDL is lost when I need to reference it elsewhere (I need to pull out the SelectedValue).
Ideas on how handle this?  I've marked the DDL with EnableViewState = true, but that doesn't resolve it.