time differences

Dear list,

I have a need for calculating differences in times. The times are from
sporting events and are in these formats:
<Totaltime>1:15.28</Totaltime>
<Totaltime>1:15.69</Totaltime>
Here it means one minute, 15 seconds and 28 hundreds of a second (or 69
hundreds of a second) so the difference here is 41 hundreds of a second (0.48
as it would say in my output)

The format could also be:
<Totaltime>1:10:15.28</Totaltime>
<Totaltime>1:11:15.69</Totaltime>
where the time means one hour, 11 minutes, 15 seconds and 28 (or 69) hundreds
of a second. The difference her should then be one minute and 41 hundreds of a
second (1:00.41)

Up until now I have done this in an external function in a program (windows
service (daemon)) that is doing all conversions for us. Problem is that a new
structure of the service has stopped the external functions from working. I
will not go back to the old structure because the new structure made the
service faster.

I am using Saxon for transformations, and I have been in contact with Mr.
Michael Kay regarding problems with external functions (thanks for all the
help!, but we have not found a solution. (dll with external functions has been
put in the GAC even without luck)

A complete solution is not necessary (although it would be nice), but some
pointers towards which direction I should go - how to solve this - would help
me a lot.

Best regards,

Trond