UserControl javascript: get control by id

[motil]

in your case this

var leftLabel = document.getElementById('<&#37;= Me.lblLeftValue.ClientID %>');
  var rightLabel = document.getElementById('<%= Me.lblRightValue.ClientID %>');

won't work, cause you need to use multiple controls in your page.
what you need to do is to get first the control id which i beleive you can get it with the sender object (did you tried what i wrote in my other post?)
and then use it as the label id, it should be something like this:

if the control id is: ctl00_MainContent_slider2_table
then this is how you'll get the wanted labels IDs:

<script type="text/javascript" id="igClientScript">
<!--

    function sliderControl_ValueChanged(sender, eventArgs) {

        var objectID =  sender.id;
       var leftLabelID = objectID.substring(0,26) + 'lblLeftValue';
       var rightLabelID = objectID.substring(0,26) + 'lblRightValue';
        var leftLabel = document.getElementById(leftLabelID );
        var rightLabel = document.getElementById(rightLabelID);

        var maxValue = sender.get_maxValueAsDouble();
        var value = eventArgs.get_newValue();
        leftLabel.innerHTML = value;
        rightLabel.innerHTML = maxValue - value;
    }// -->
</script>