Mean frequency and Amplitude calculation

Hello everyone, I am loading a text file which has has a big data (comprising of 3 columns and multiple rows). First and second column represents (Time and Electrical activity) and on the 3rd column there are comments at different rows. I need to find only mean frequency and amplitude in a way such that i calculate 5 seconds mean freq. before the first comment and then for next 5 sec + next 5sec (if the second comment comes before the next 5 seconds, we calculate the mean freq for the remaining time and not full for the 5 seconds). After the second comment we again calculate the mean freq for next 5 sec + 5 sec. I have attached a graphical representation explanation of the above question as it may be difficult to understand. I am also attaching my data file and script. (Emma.txt is the file i am loading : trial.txt is my matlab code so far : Data.jpg is the graphical representation of my question)

Thank you