Average time calculation in views

I need help with average time calculation in drupal views. I use HMS field module ([login to view URL]) to register handling times of tasks. I need help with calculation of average time of tasks and get the result in time format (mm:ss) for example. number of task 10 total handlingtime 00:45:00 = 4:30 I can do this with help of math expression but then i get the result in secons (4,5) but i need this in time format. I want a solution that I can easily reuse in other views reports. I also want to do this calculation in a total row of the report. For example. task1 - count of task2 - total handling time - avg handling time task2 - count of task2 - total handling time - avg handling time task3 - count of task3 - total handling time - avg handling time Total - count of task1+2+3 - total handling time of all task - avg handling time