mileage expenses form formulas

Hi everyone.
I have created a mileage expenses form in which the start mileage is placed in say column H, the end mileage in column I, and the actual mileage done in column J
I have always used a simple manual calculation to give the mileage figure by subtracting say H3 from I4 but is there anyway i can do this automatically, bearing in mind there is usually a different number of visits each day therefore the number of rows are not constant between days.

I am not sure if my problem is unable to be solved or if it it too simple to spare the time to reply?

I would be really grateful for any feedback whatsoever.

thanks in anticipation.

Wayne

It would be great if one of you experts could respond please?

It seemed like a simple problem to solve after looking at some of the things you guys have been achieving on here. I would just like to know if it can be done, IF you could tell me how it would be even better.

Thanks anyway.