Activities (few working days in a row)

I'm using this excellent tool for scheduling seminars: making relations between students, their companies (if they work), and teachers (for a certain seminar in given period of time). I'd like to put starting and ending date of a certain activity with entering just the total duration of hours in between. For example:

student: John Doe
company: SONY

seminar: Project Management II
FROM: 8th Aug, 2006
TO: 21st Aug, 2006.
total duration: 120hrs
location: Yale Uni., New Haven
building: 135
teacher: Jane Smith, prof.

It would be very useful if I could be able to put relations such as:

Student "John Doe" from "SONY" Company, participated on the seminar "Project Management II" from 8th Aug, 2006 to 21st Aug, 2006. ( total duration: 120hrs) where the teacher was Jane Smith.

Now, "activities" support just one date and the total duration of hours for that specific day, which doesn't suit our needs, because one activity could be a block of several working days in a row.