Need Help Debugging Script/Error in Script - Sliding menu

var sliderIntervalId = 0;
var sliderHeight = 1;
var sliding = false;
var slideSpeed = 10;
var elementName = "";
var getHeight = 0;

function Slide(element)
{
   elementName = element;
   getHeight = document.getElementById(elementName).offsetHeight;  
   sliderHeight = getHeight
   if(sliding)
      return;
   sliding = true;
   if(sliderHeight == getHeight )
      sliderIntervalId = setInterval('SlideUpRun()', 30);
   else
      sliderIntervalId = setInterval('SlideDownRun()', 30);
}

function SlideUpRun()
{
   slider = document.getElementById(elementName);
   if(sliderHeight <= 0)
   {
   	  alert('slideup_true' + sliderHeight)
      sliding = false;
      sliderHeight = 0;
      slider.style.height = '0px';
      clearInterval(sliderIntervalId);
   }
   else
   {
   	alert(sliderHeight)
      sliderHeight -= slideSpeed;
      if(sliderHeight < 0)
         sliderHeight = 0;
      slider.style.height = sliderHeight + 'px';
   }
}