which formula to use?

I have created a spreadsheet for the turnaround time of stat radiographs. In one column I type the time the exam was sent to be read, then in the next column I type the time the results were recieved. In the third column I have used a formula to tell me how long in hours and minutes it took to get the results. Now I need to make a chart using those numbers in the third column. Instead of me counting the results, I would like to generate a chart that tells me how many exams came back in 0:00-0:30mins, how many in 0:31-1:00, how many in 1:01-1:30, and so forth, (using 30 minute intervals). I can not seem to figure out what to use to generate this. I was trying to generate it in a new spreadsheet then create a chart from that, but if someone knowd an easier way, or anyway, that would be great.

Thank you,
Meg

That is very helpful and exactly what I was trying to do. How did you set up the interval & no. box?

Hi VBA, in your formula above, what purpose is served by the -- immediately following your open paren?

I'm still trying to get a handle on how to use the sumproduct function,

thanks