Hi,
First you need to import the data to MATLAB, you can use 'readmatrix', refer to this documentation for more information about this function.
After you have the data in a matrix you can use 'if' statement to check if your condition is satisfied and then use 'max' & 'min' functions to do the calculation you require. Refer to below documentation for more information about these functions-
For example the code would look similar to the following
>> mat = readmatrix('my_data.csv');
>> if(Y!=0)
>> var = max(mat(:,1)) - min(mat(:,1));
>> end
