Adding Lanes to a Process

Hi,

I've modelled a Collaboration Diagram without Lanes.

Now I'd like to add Lanes to one of the Pools/ Process. The Problem here: It's easy to create an empty Pool and add Lanes by drag'ndrop or context menu but it seems impossible to add Lanes to an existing Pool containing a Process / any symbols.

Do I have to create a new Pool with Lanes and move the Process and Messageflows or is there an easy solution?

Thank you

Christian