Characters Count in a Text Box

This java code sample shows how to find the Characters Count in a Text Box.
Call to JavaScript Method on Different Event (onkeypress,onkeyup,onkeydown,onPaste) of TextBox

private void AddScriptCounter()
    {        
        txtMessage.Attributes.Add("onkeypress", "CountCharactersGeneral('" + txtMessage.ClientID + 

"','inputTxtMessageCountAge'," + 4000 + ")");
        txtMessage.Attributes.Add("onkeyup", "CountCharactersGeneral('" + txtMessage.ClientID + 
"','inputTxtMessageCountAge'," + 4000 + ")");
        txtMessage.Attributes.Add("onkeydown", "CountCharactersGeneral('" + txtMessage.ClientID + 
"','inputTxtMessageCountAge'," + 4000 + ")");
        txtMessage.Attributes.Add("onPaste", "CountCharactersGeneral('" + txtMessage.ClientID + 
"','inputTxtMessageCountAge'," + 4000 + ")");
    }

Java Script Code
Javascript Method to COunt the Character and Restrict to the maximum charcter that can be entered into a textbox.
sourceTextBox (Source Text Box)
displayControl (Control where you want to diplay remaing characters count)
maxLength (Maximum number of Character that can be entered into the Source Text Box.)

function CountCharactersGeneral(sourceTextBox, displayControl, maxLength)
{

    if(sourceTextBox != null && displayControl != null)
    {
		sourceTextBox = document.getElementById(sourceTextBox);
                displayControl = document.getElementById(displayControl);
                if(sourceTextBox != null)
                {
                    var len = sourceTextBox.value.length
                    if (len<=maxLength) //if entered charcters less than the Maximum Limit.
                    {
                        //Shows Number of characters Remaining 
                        displayControl.innerHTML = maxLength -len + " Character(s) remaining.";
                    }
                    else
                    {
                        sourceTextBox.value = sourceTextBox.value.substring(0, maxLength);
                        return false;
                    }
               }
    }
}

Thanks & Regards
Lakhan Pal Garg