If you want to Reference external assemblies that are not part of Data Sync with Dynamic Columns or Project Automation you can.
There are two steps:
Open DS2 and navigate to file menu item then select Properties. This will display the Project Properties dialog.
Select the Assemblies Property which will show the list of the Assemblies references.
Click 'Add' enter the path to the Assembly for example:
C:\Program Files\Microsoft SDKs\Windows Azure\.NET SDK\v2.3\bin\Microsoft.WindowsAzure.StorageClient.dll