[jQuery] Slider - value = function

Hi peoples.
I just wanted to ask... is is a bug that I cant use a function as
value of a Slider (UI) ?
fx:
$("#soundControl #setVolume").slider({
    range: "min",
    min: -3,
    max: 103,
    value: ytplayer.getVolume(),
});
This wont even show the slider because of the value of value
(ytplayer.getVolume())
What can I to make this work?