function printDuration() {
  var now = parallel.currTimeState.activeDur;
  alert(now.toFixed(2));
}

And here is the Demo:

<INPUT TYPE="button" value="Show Active Duration" onclick="printDuration()">
<t:PAR CLASS="time" ID="parallel" REPEATCOUNT="indefinite">
    <H1 ID="hdg1" CLASS="time" STYLE="color:red;" 
	TIMEACTION="style" BEGIN="0" DUR="3">Heading 1</H1>
    <H2 ID="hdg2" CLASS="time" STYLE="color:red;" 
	TIMEACTION="style" BEGIN="0" DUR="3">Heading 2</H2>
    <H3 ID="hdg3" CLASS="time" STYLE="color:blue;" 
	TIMEACTION="style" BEGIN="3" DUR="3">Heading 3</H3>
    <H4 ID="hdg4" CLASS="time" STYLE="color:blue;" 
	TIMEACTION="style" BEGIN="3" DUR="3">Heading 4</H4>
    <H5 ID="hdg5" CLASS="time" STYLE="color:green;" 
	TIMEACTION="style" BEGIN="6" DUR="3">Heading 5</H5>
    <H6 ID="hdg6" CLASS="time" STYLE="color:green;" 
	TIMEACTION="style" BEGIN="6" DUR="3">Heading 6</H6>
</t:PAR>

Learn more about HTML+TIME in Column 67, Introduction to HTML+TIME.

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