Contextual Menu popup on row of WebListBox?

RIght now I have my mouse up event tied to populating another view.
Now I’m trying to do a right click and I’m not sure if that can be done.
What are my options?

I want to change the contextual menu on the row mousedown event depending on what the contents of the row # is.
Is that ok? The example show the contextual menu being constructed in the shown event.