add: document.getElementById("daysEnd").disabled = locked || !leaveMsgsChecked; 
context: function setupAgeMsgOnServerUI(){    var leaveMsgsChecked = document.getElementById("pop3.leaveMessagesOnServer").checked;   var checked = document.getElementById("pop3.deleteByAgeFromServer").checked;   var locked = getAccountValueIsLocked(document.getElementById("pop3.deleteByAgeFromServer"));   document.getElementById("pop3.deleteByAgeFromServer").disabled = locked || !leaveMsgsChecked;   document.getElementById("pop3.numDaysToLeaveOnServer").disabled = locked || !checked || !leaveMsgsChecked;}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/0c6a8bff6a4b0eec152d770f6686c7616568058d/am-server.js/buggy/mailnews/base/prefs/resources/content/am-server.js