Creating a faders on osc

hello i been trying to make a custom fader for a video player control the fade in effects works like this Image may be NSFW.
Clik here to view.

    if (fadeIn==true) {
    times =ofGetElapsedTimef();
    float phase = 1 * times;
    float value = phase + kx;

    if (kx<255) {
        kx++;
    }
    ofxOscMessage m;
    m.setAddress( "/ch1/set_alpha" );
    m.addIntArg( kx );
    oscSender.sendMessage( m );
}

it is control by pressing a key
but when im trying to do the same for fade out the alpha channel gets to 0 immediately and can fade in again can someone help what i wanna do is to control the time or seconds to get from 0 to 255 in the alpha channel and from 255 to 0
help!!!