Duplicate default:modified & rendererd wth "lastmodified" Property Rend.?

I try to create a new property said name new_modified which is the duplication of the property metadata - default:modiifed (cm_modified).

The only thing I change in the new property - new_,modified is switching the Type from "TimeStamp" to "Date". This work fine for changing the Date format.

But here is the problem:

Initially, I thought the "lastmodified" property renderer will automatically assign the current date value to the new_modified property (when I assign this property to a km resource/document, open & edit the document).

I decoded the source of lastmodified property renderer:

com.sapportals.wcm.control.util.PropertyRendererLastModified.

Here is the renderProperty method:

public Component renderProperty(IProperty property, IResource res, int maxLength)
    {        PropertyType propType = null;        TextView resultText = null;        String result = null;        try        {            <b>if(property == null)            {                property = res.getProperty(PropertyName.createLastModified());</b>                if(property == null)                {                    if(log.beDebug())                        log.debugT("Could not retrieve Property <" + PropertyName.createLastModified() + "> for resource <" + res + ">");                    return null;                }            }        }        catch(Exception e)        {            CatchBlockHandler.handle("PropertyRendererLastModified", "Exception", e, false, false);            log.errorT("Caught exception when trying to render property <" + property + "> for resource <" + res + ">" + LoggingFormatter.extractCallstack(e));            return null;        }        propType = property.getType();        if(propType == PropertyType.DATE)            result = DateFormatUtil.format(property, res.getContext());        else            result = property.getStringValue();        if(result == null || result.length() == 0)        {            if(log.beDebug())                log.debugT("The property <" + PropertyName.createLastModified() + "> for resource <" + res + "> returned no value and will not be rendered.");            return null;        }        resultText = new TextView("PropertyRendererLastModified");        if(is508Required())            resultText.setTooltip(PropertyRenderUtil.get508PropertyTooltip(property, result, res.getContext().getLocale()));        else            resultText.setTooltip(result);        if(maxLength > 0 && result.length() > maxLength)            result = result.substring(0, maxLength);        resultText.setText(result);        resultText.setWrapping(true);        return resultText;    }

Seems like they only assign the new modified value when the check that the property==null.

Isn't that this property renderer will set a new current Date value to new_modified property every time we edit the document?

If not, how do I set the new_modified to have the value of modified every time we edit the document.

Thanks for advise.

Regards,

Kent