Excel can also run client-side Windows Workflows. The DocumentParts activity encapsulates the Open Xml document stream as a document context. RangePart activities inherit from ContentPart and encapsulate Excel cell range related Open Xml.
The Office host acts as a Tracking Participant or Event Subscriber which decouples the workflow logic from the client host. In the figure below, the workflow emits tracking state events. An Excel Add-in filters the RangePartActivity state events and inserts
the cell values.