Compare timestamps and output most recent value in child elements to parent element

From a varying number of child elements (all sharing the same template), I want to find the most recent timestamp of a same template-based attribute, and output the value with timestamp to an attribute in the parent element. In addition, constantly (event-triggered/periodic) comparing the timestamps of these child element attributes and always output the "newest" value to the parent element attribute. Example: From 3 child elements, all sharing the same template with attribute "ALARM", I want to have the most recent value comparing the 3 "ALARM"s, and have this timestamp and value in an attribute in the parent element. Suggestions for enhancement: - Function in Rollup Analysis which compares timestamps of template based attributes and outputs the most recent timestamp (with value!).