var str = 'div_pr_';
var totalProducts;
var currentStartIndex = 1;
for(totalProducts=1;;totalProducts++)
{
    if(document.getElementById(str + totalProducts) == null)
    {
    	totalProducts -= 1;
        break;
    }
}
function ShowPrev()
{
    if(currentStartIndex > 1)
    {
        currentStartIndex = currentStartIndex - 1; 
        ShowProductRange(currentStartIndex,currentStartIndex+4);                   
    }
    //else
    //{
       // alert("End of List");        
    //}
    return false;
}
function ShowNext()
{
    if(currentStartIndex <= totalProducts - 5)
    {
        currentStartIndex = currentStartIndex + 1;
        ShowProductRange(currentStartIndex,currentStartIndex+4);
    }
    //else
    //{
        //alert("End of List");        
    //}
    return false;
}
function ShowProductRange(startIndex,endIndex)
{ 
    for(var i=1;;i++)
    {
        if(document.getElementById(str + i) != null)
        {
            if(i>= startIndex && i<=endIndex)
            {
                document.getElementById(str + i).style.display = "block";
            }
            else
            {
                document.getElementById(str + i).style.display = "none";
            }
        }
        else
        {
            break;
        }
    }
}