Very complicated calculation of total hours worked (PLEASE HELP)

Hi. I have a spreadsheet that shows the amount of time that somebody worked over the course of several years. The spreadsheet is about 30,000 rows long and very poorly organized (more on this below). I need to calculate the hours worked by this individual each day over the course of all the years shown on the spreadsheet, but there are NOT separate columns for time clocked in and time clocked out. If there were separate columns for those values, I could calculate the total hours worked on the first day/row, and then I could drag the formula down the entire spreadsheet.

Unfortunately, as I said, there are not separate columns for the clock-in and clock-out times. Instead there is one column for both times. To make matters worse, the column that shows times does not only show time clocked in and time clocked out; it also shows the times at which various work tasks were performed throughout the day (between the clock-in and clock-out times).

Anyway, my boss wants me to figure out the total number of work hours recorded on the spreadsheet, and I have no idea how to proceed. The column that shows times (clocked in, clocked out, etc.) is right next to a column that shows the date (which is entered as a number rather than a date). Also, the date is written in the format YYYYMMDD, just to make things more confusing. So this is what the spreadsheet looks like:

DATE | TIME | ACTIVITY
20080507 | 9:30 | clock-in/work task #1
20080507 | 11:30 | work task #2
20080507 | 2:30 | work task #3
20080507 | 4:30 | clock-out
20080508 | 9:30 | clock-in/work task #1
20080508 | 11:30 | work task #2
20080508 | 2:30 | work task #3
20080508 | 4:30 | clock-out
20080509 | 9:30 | clock-in/work task #1
20080509 | 11:30 | work task #2
20080509 | 2:30 | work task #3
20080509 | 4:30 | clock-out

(NOTE: The actual spreadsheet contains extreme variation between the days in terms of the hours worked on each day.)

Anyway, given the strange format of this spreadsheet, I have no idea how to automatically calculate the total hours worked down the entire spreadsheet. The only thing that I can do is create formulas for each day (one day at a time) and then add up all the hours once I've calculated them day-by-day. The process would take months, which is too long for the demands of my boss. By the way, I have to do this for 7 other spreadsheets that are also about 30,000 rows long.

Is there any way to create formulas that can 1) divide the rows into segments based on the DATE values 2) automatically calculate the total time elapsed within each segment/day (using the first and last time values for each segment/day, which would represent, respectively, time clocked-in and time clocked-out)?

As you can see, this problem far exceeds my Excel capabilities. I truly appreciate any and all help that you guys can offer. Thank you.

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Welcome to the Forum, unfortunately:

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