Thanks for the responses. After trying a few things out this morning, I have found that the following works.

select convert (varchar(30),cast (Time2 as datetime) - cast (Time1 as datetime),108)...

I have had a quick look at the raw data and the negative valuse are occurring where the minutes or seconds value for the second time is lower than that...

Thank you for such a promt response.

Using the datediff functions suggested I have managed to get some data out, however, some of the results are a little unexpected with...