function checkEnterKey(objEvent)
{
    // objEvent is event object passed from function invocation.
    var strCharacterCode;

    if (objEvent && objEvent.which)
    { 
        // Character code is contained in NN4's which property.
        objEvent = objEvent;
        strCharacterCode = objEvent.which;
    }
    else
    {
        // Character code is contained in IE's keyCode property.
        objEvent = event;
        strCharacterCode = objEvent.keyCode;
    }

    if (strCharacterCode == 13)
    { 
        // Character code is equal to ascii 13 (enter key)
        document.getElementById("enterKeypressField").value = "true";
    }

    return;
}