All:

I'm working on a demonstration, and having an issue getting the slider values to cooperate. The code below isolates the issue. I'd like for the a value to reset to the new initial value when I click the button. In this code, the slider boundaries change (which is good), but the existing a value is inherited rather than resetting to the new initial value.

Appreciate any and all advice!

Manipulate[

 a,

 {{b, 1, "direction"}, {1 -> "Left to Right", 2 -> "Right to Left"}},
 PaneSelector[{
   1 -> Control[{{a, -1, "x"}, -1, 1.99999, Appearance -> "Labeled"}],
   2 -> Control[{{a, 4, "x"}, 2.00001, 4, Appearance -> "Labeled"}]
   }, Dynamic[b]],

 TrackedSymbols -> {a, b}
 ]