[O] Adding times in a table

[gmx]

Hi,

I've a table like this one :

	Time for each task
1	00:53
2	03:12
Total

Which formula should I use to obtain the result (hh:mm) of the sum of the times in the last cell of column 2? I tried this one :  #+TBLFM: @>$2=vsum(@2$2..@3$2). Result : 1:4

Each of these times are calculated by org-mode for a given task. I don't know if it's possible that they could be imported directly into the table: you'll tell me about it.

Thank you much

Fred (real newbie with org-mode),