The input array to the function 'fft' can be either a vector or a matrix. Firstly, you can create a table using the data in the excel sheet with the function 'readtable'.
Then, you can choose only those rows and columns for which you want to analyse the data.
For example, let A be the table with the data. To use rows 1 to 5000 and all columns, the syntax is:
To use rows 2500 to 10000 and columns 2 to 4, the syntax is:
Y = fft(A(2500:10000,2:4));
For additional information on the functions used here, refer to the following links:
Hope this helps!