Can callback actions return a value?

I have a widget that consists of a FormField and a button.
It has two parameters : a value and a callback.
The callback is executed when the button is pressed.

The callback's goal is to display a list of values and once the selected value has been picked , the FormField will be updated with the value returned from the callback. The callback does execute, but I see no way to get the

The alternative is to use a global variable, but that defeats the purpose of creating a widget.