Need help finding info within a large matrix

So I'm setting up a gui to simulate a test with multiple sensors. The nature of the test is such that 1 of 3 sensors will be tripped first and this will be recorded along with a value for speed. There is also a counter for how many times each sensor has been tripped and the total count. The way the data is recorded is:

Data = [Data [Speed; t; FirstSensorTripped; SensorOneCount; SensorTwoCount; SensorThreeCount; TotalCount]]

I need to help with creating a loop that will see when the count for each sensor has exceeded a certain value... lets say 3... and will then be able to take the average of the speed recorded for when each individual sensor is tripped. To clarify, there will be three average speeds: one that is accociated with the first sensor being tripped first, one that is associated with the second sensor being tripped first, and same with the third.

I appreciate any kind of guidance. I think I just need someone to point me in the direction of the right commands to use to find info within matrices.