dynamic - Dynamically show usage

As the title states I would like to dynamically show ::usage on several functions.

Let's consider two functions here:

funlist={Plot,Plot3D};

Thus I do:

Input[
  Panel[
   PopupMenu[Dynamic@whichfun, funlist], "usage should be here"], 
  Dynamic@whichfun]

Instead of "usage should be here" I obviously tried (Dynamic@whichfun)::usage but it's complaining that the Head is not a Symbol, so I tried to convert it to a Symbol but it still fails.

Thus the question is:

How can I convert Dynamic@whichfun in order to be able to have its usage?

Answer

This is the problem with evaluation, since MessageName is HoldFirst. You can use e.g.

Dynamic[MessageName @@ {whichfun, "usage"}]

or

Dynamic @ MessageName[Evaluate[whichfun], "usage"]

in place of "usage should be here".