how do you display time correctly using System.currentTimeMillis();

[peahead]

I am using a timer routine which I obtained from the net. This is the code:

long start = System.currentTimeMillis();
textAreaGameInfo.append(strBuf.toString());
long elapsed = System.currentTimeMillis() - start;

How can I force the correct display of time as follows:
If 0 seconds or less it should show 0.142 milliseconds
If 0 seconds or greater it should show 1.42 seconds
If 1 minute or greater it should show 1min 42 seconds

Thanks