// Simple helper to return the "exMaxLen" attribute for
// the specified field. Using "getAttribute" won't work
// with Firefox.
function GetMaxLength(targetField)
{
return targetField.exMaxLen;
}

//
// Limit the text input in the specified field.
//
function LimitInput(targetField, sourceEvent)
{
    var isPermittedKeystroke;
    var enteredKeystroke;
    var maximumFieldLength;
    var currentFieldLength;
    var inputAllowed = true;
    var selectionLength = parseInt(GetSelectionLength(targetField));
    
    if ( GetMaxLength(targetField) != null )
    {
     // Get the current and maximum field length
     currentFieldLength = parseInt(targetField.value.length);
        maximumFieldLength = parseInt(GetMaxLength(targetField));

        // Allow non-printing, arrow and delete keys
enteredKeystroke = window.event ? sourceEvent.keyCode : sourceEvent.which;
        isPermittedKeystroke = ((enteredKeystroke < 32)                                // Non printing
                     ||(enteredKeystroke >= 33 && enteredKeystroke <= 40)    // Page Up, Down, Home, End, Arrow
                     ||(enteredKeystroke == 46))                            // Delete

        // Decide whether the keystroke is allowed to proceed
        if ( !isPermittedKeystroke )
        {
            if ( ( currentFieldLength - selectionLength ) >= maximumFieldLength ) 
            {
                inputAllowed = false;
            }
        }
        
        // Force a trim of the textarea contents if necessary
        if ( currentFieldLength > maximumFieldLength )
        {
            targetField.value = targetField.value.substring(0, maximumFieldLength)
        }
    } 
    
    sourceEvent.returnValue = inputAllowed;
    return (inputAllowed);
}

//
// Limit the text input in the specified field.
//
function LimitPaste(targetField, sourceEvent)
{
    var clipboardText;
    var resultantLength;
    var maximumFieldLength;
    var currentFieldLength;
    var pasteAllowed = true;
    var selectionLength = GetSelectionLength(targetField);

    if ( GetMaxLength(targetField) != null )
    {
     // Get the current and maximum field length
     currentFieldLength = parseInt(targetField.value.length);
        maximumFieldLength = parseInt(GetMaxLength(targetField));

        clipboardText = window.clipboardData.getData("Text");
        resultantLength = currentFieldLength + clipboardText.length - selectionLength;
        if ( resultantLength > maximumFieldLength)
        {
            pasteAllowed = false;
        }    
    }    
    
    sourceEvent.returnValue = pasteAllowed;
    return (pasteAllowed);
}

//
// Returns the number of selected characters in 
// the specified element
//
function GetSelectionLength(targetField)
{
    if ( targetField.selectionStart == undefined )
    {
        return document.selection.createRange().text.length;
    }
    else
    {
        return (targetField.selectionEnd - targetField.selectionStart);
    }
}