I have 2 problems with a time sheet that I am working on.

The first is that I cannot get exel to show negetive hour/minute values. For instance - We normally finish work at 00:30 (A1) but finished at 23:45(B1). The calculation I am using is =SUM(B1-A1). This is giving a value of 23:15 instead of -00:45. However if we finished after 00:30 the value is correct.

Next - if we work 28hrs over time then we are paid for example 10.53 per hour for the first 20hrs and then 14.04 for the next 8hrs. What would the formular be to show the total amount due?

Many thanks