Do you mean that you want to add up (sum) all the hours and minutes
from this column? I'm not sure why you would want to do this, but you
could enter this formula somewhere:

=sum(A1:A70)

and then select the cell and Format | Cell | Number (tab), scroll down
to Custom and enter [h]:mm as the format. This will give you total
hours in a form like 37:55 (i.e. it does not wrap at 24 hours)

I hope this is what you want - post back if not.

Pete