[FieldTrip] using triggers building my own function

[moran abilea]

hi everyone,
so i'm trying to create my own function for using triggers with EEG raw
data.
i used this tutorial:
http://www.fieldtriptoolbox.org/tutorial/preprocessing

my question is if i can somehow specify the time i want to record my EEG
data?
for example i would like my function to get 'time' as parameter to the
function and returns the EEG raw data of this specific time+one second.
if so, can some one give me a piece of code for example to understand what
to do?

also 2 more little questions:
1. cfg.trialdef.eventvalue = [3 5 9]; what does the 3 5 9 stands for? i
don't understand what is the meaning of those (or any other) numbers. can i
get definition for what is event value?
2. cfg.trialdef.prestim    = 1;
cfg.trialdef.poststim   = 2;
does it means it takes exactly one second for the buffer to give me the EEG
raw data? or does it means wait one second and then take the data from the
buffer or something like that (1 second the trigger will "pop out" and
finish taking the data from the buffer after 2 seconds)

the triggers are new to me, so i have some problems to understand the
concept of it, thus my questions for you guys.

i hope i explained myself as clear as possible, i really would like to
understand what i'm doing.

regards,
Moran Abilea
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