Using JavaScript to show next button when slider button has been moved

Hi there,

In my Qualtrics survey I am trying to get the next button to appear either after participants had made a response on a slider or autoadvance after 5 seconds. I've only been trying to figure out how to do this by using the mousedown command as I'm not sure how I'd code dragging a slider. This is what I have so far, its advancing after 5 seconds but the next button isn't appearing. Any help would be much appreciated!

var mouseDown = 0;
document.body.onmousedown = function() { 
 ++mouseDown;
}
document.body.onmouseup = function() {
 --mouseDown;
}

Qualtrics.SurveyEngine.addOnload(function() 
{
this.hideNextButton();

if (mouseDown) {
this.showNextButton();
} else {
this.clickNextButton.delay(5);
} 


});

Qualtrics.SurveyEngine.addOnReady(function()
{
/*Place your JavaScript here to run when the page is fully displayed*/

});

Qualtrics.SurveyEngine.addOnUnload(function()
{
/*Place your JavaScript here to run when the page is unloaded*/

});

Please note I've never used JavaScript before!