RTD servers are event driven so when I get new data for a specific
topic how do I update the indiviual topic? Is my only choice to call
RefreshData? Does refresh data update all topics?

What I am planning on doing is associating an event with a topic so
that when a new value comes in about a specific topic it calls
RefreshData. My concern was that I will be calling RefreshData a lot
when I really only want to update a specific piece of data.

I guess my other option is to have a method that is called when a piece
of data is updated which sets a flag indicating some piece of data has
changed. Then I call another method every x seconds/minutes and if it
sees the flag set it calls RefreshData. Does that sound right?