One of the most popular features of Open XML among developers is the concept of binding content controls (structured document tags) to custom XML nodes. This is a powerful concept that allows for simple integration between existing XML instances of business data and the rich look and feel of typical Open XML word-processing documents, while keeping the data and presentation details cleanly separated.
Once developers start thinking creatively about how to use content controls, however, there's one thing that can get a bit confusing: how to deal with repeating data structures. It's a simple matter to have a fixed set of content controls bound to a fixed set of custom XML nodes, but in many scenarios you'll want to generate a document with a table that contains a variable number of rows, to be determined dynamically at runtime by the data itself.
My colleague Dimitris Koutsanastasis, a developer evangelist in Greece, has put together an interesting demonstration of how to handle this situation over on OpenXmlDeveloper.org entitled "Dynamic production of repeating context controls by a WCF service." It's packaged as a WCF service with a Winform front end, but the underlying architecture is applicable to any scenario where you need to dynamically generate content controls. The article contains complete source code.