Another way will be to do that with a computed field in the Boxi Universe.
Then you can write direct SQL to archive your need.
Assuming you store you duration as second (unixtimestamp) will be something like:
CONVERT (varchar, , (Zresponse_Time /86400)) + ': '+ CONVERT(varchar, DATEADD(ss,Zresponse_Time, 0), 108);
will return the days/hours/minutes/second in the format like 02 days 10:00:20. you can of course extend from that...
There is many different way to archive this in TSQL and you can found many different examples on internet on how to do that.
My 2 cents
/J