I need to create a list column which contains external data (from BDC). The field has to contain multiple values. But I haven't found a way how to make a external-data-field take multiple values.
Creating such a multi-value field is possible by using the Column-Properties "allow multiple selections" in a user content type. However, creating a column using external data I do not have the ability to add a multi-value column.
It should look like this, just from a external data source (BDC/BCS):

Does anyone know how to handle such a situation?
My Environment: SharePoint 2010, Visual studio 2010, SharePoint Designer
