function GetMaxLength(targetField) {
    if (targetField.exMaxLen != null)
        return targetField.exMaxLen; //IE
    else
        return targetField.getAttribute('exMaxLen'); //FireFox
}

//
// 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)
					          || (enteredKeystroke >= 33 && enteredKeystroke <= 40)
					          || (enteredKeystroke == 46))

        // 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);
    }
}