Code you sent works fine! I also made replacements you suggested:
String cmd = param[0].asStr(); //eg. 'int60'
String kwd = "int"; //keyword
if (cmd.length() > kwd.length() && cmd.substring(0,kwd.length()).equalsIgnoreCase(kwd) && cmd.substring(kwd.length()).toInt() > 0)
{
timer.deleteTimer(timerID);
timerID = timer.setInterval(cmd.substring(kwd.length()).toInt() * 1000L, notifyUptime);
}
Have a nice day!