output files written at particular times and sampling time problems

Hello,

I am modelling a system in simulink with large excel sheet as input. I have few questions:

1. The first column of the data excel field represent the time, 1 row for 1 hour. I have first used a function to read the file, in which I ask the model to read 1 row for 3600 seconds. But I have seen that one can use spreadsheet. What is the better way?
2. I use variable time step for all the model, so the resulting file (I have written a script in matlab to put the results into an excel file) is very big and time is like (1.24 2.38 3.6...) , I mean, it's not written every second; so I tried to change this and in the output pad in the configuration panel, I put the option to write output at specific values only, every 300 seconds (for this I put 300*(1:8928), to cover one month), but doing this it takes too much time (many hours ...). Is there another way to deal with that? Moreover, I would like to write the results every second so I could do a media on the 300seconds through excel....but already every 300 seconds takes hours and hours.....

I am sorry if these questions have already been mentioned, I have done so many research in the forum these days, but I couldn't find anwers to that.

I have never used files of input/output before.

And I also meet problems with the spreadsheet way, where I define a sampling time of 3600s and give me problems because the rest of the model is continuous.

I would really be happy for any help or at least, some hints... In particular, could someone help me understand this sampling time, personnally, I haven't a lot of experience with Matlab/Simulink, and the help is really confusing for understanding

Thank you

Christine