Is it possible to show a fixed text such as *"updating..."* instead of the last result shown, when `Manipulate` is re-evaluating an expression (in a slow evaluation context)? How to do it?

More precisely, I have a `Button` element in the set of controls, and it is the action triggered by the button the one that slows down the process, and *not* the results shown in the `Manipulate` sentence themselves.

This could be a MWE for what I mean:

    Manipulate[result,
     {{x, 5}, 0, 10, 1, Appearance -> {"Labeled"}, AppearanceElements -> None},
     {{y, 5}, 0, 10, 1, Appearance -> {"Labeled"}, AppearanceElements -> None},
     Button["Calculate", Pause[2]; result = x + y],
     TrackedSymbols :> {result},
     Initialization -> Clear[result, x, y]]

In this example, the values for two integer numbers `x` and `y` are selected using their respective slider controls, and then a button is used to perform some calculations based on them. Finally, results based on those calculations are shown using `Manipulate`.

So, regarding this example, my question is: how can I show the text *"updating..."* while the button is *thinking*?

If you think there would be an easier solution in case it was not the button but the expression to be shown by `Manipulate` the one that takes some long time to be executed, I think I could also modify my real problem to be like that. The MWE could be like this:

    Manipulate[Pause[2]; parameters[[1]] + parameters[[2]],
     {{a, 5}, 0, 10, 1, Appearance -> {"Labeled"}, AppearanceElements -> None},
     {{b, 5}, 0, 10, 1, Appearance -> {"Labeled"}, AppearanceElements -> None},
     Button["Calculate", parameters = {a, b}], 
     TrackedSymbols :> {parameters}, 
     Initialization -> (Clear[a, b, parameters]; parameters = {5, 5})]

It would be also OK if the text *"updating..."* appeared *in the button*, temporarily replacing the *"Calculate"* text. It would be a little bit strange, but also valid.

I look forward to your solutions.