It did sound similar, I didn't find that thread yesterday while searching.
But I ended up doing what that link I referred to said, using the OnIdle() sub. So I'm just setting a boolean value (allowedToUpdate=True) in the context handler now, and in the OnIdle sub I'll do the trend updating if allowedToUpdate=True.
The thing I found a bit strange with the ContextHandler is that I would expect it to run after the context had changed - and all the context sensitive values in the display had been updated. I would think that it would be more useful. In reality, this should really be called BeforeContextChanged(…) the same way you have the other Before- and After- events for Display.
Or at least a new AfterContextChanged(...) should be added.