How do you create and plots subsets of array data?

Suppose I have a table of values for various events.

Event  Event #  Time start   Time stop   Velocity  Acceleration 
A          1         400        405          10           3
B          1         410        411           12          4    
A          2         415        419           11          3.5
.... etc

I want to create a bar graph of how many times event A occurs over the whole time interval, so my questions are:

1) How do I create a subset of this table for event A with only time start and event # information?

Event  Event #  Time start   
A          1         400          
A          2         412
A          3         440
A          4         460

2) How do I create a new Time column that is in minutes and starts at 0?

Event  Event #  Time start   Time adjusted
A          1         400          0
A          2         412          .2
A          3         440          .66
A          4         460           1

3) How do I create another subset of this data, with only data from each one minute mark?

Event  Event #     Time adjusted
A          1                0
A          4                1
A          7                2

4) Finally, I want to plot this data as a bar graph.