Point A to point B timer with PC output

[Freak]

I have been asked to come up with a way of counting how long it takes to get
from point a to point b keeping in mind that there maybe 10 people in the
middle of the loop and to display the length of time they have been waiting
while at point B on a seven segment display, then on to the next person

triggering is accurately being triggered by a relay pulling closed

but all this need a output to the serial port with a caruture every time
point A is triggered and every time B it triggered

somthing as simple as a "a" for point A and a "A" for point B is all thats
need for logging purposes ( what to be able to log trends and when service
delays happen )

I have alwas had a interesed in electronics and hardware but never have
atempted somthing like this, any ideas and do you thing I have bitten of
more then I can chew in this first big attempt

Thanks For any imput

Phill