calculation formula

[Jaime]

I am trying to create formula that first calculates the difference between to
time fields first and afterwards, I want it to divide by the total of records
by incident:

= Sum ([Beginning Time])-Sum ([Ending Time]) / Count ([Incident])
= Count ([Incident])
= Sum ([Beginning Time])-Sum ([Ending Time]) / Count ([Incident])

If I run each one individually the total are correct, but when I combine it
the total are uncoordinated. I know it has to do in part with the field
format but I just cannot make seem to work.