Fortran Help- maximum values

Hello I am currently working on a program that will take the values from a .csv file containing multiple data and analyzing them. The file can be found here: https://docs.google.com/file/d/0BzuDEPd26OcheVhiWl Z3STlZU0k/edit?usp=sharing The data in question starts in row 11 and is in the first 4 columns. In my program I have labeled these: rvar, ivar1, ivar2, ivar3. Rvar is the value corresponding to a time value in microseconds after start of recording whereas ivar1,ivar2,and ivar3 correspond to the value of the acceleration at that point. I have already calculated the average value of each of these columns.

My question is- how do I find the maximum value for ivar1, ivar2 and ivar3 (separately)?

My current code is below:

program WSUPhys_csv
  implicit none

  integer :: stat, num_lines, ivar1, ivar2, ivar3
  real :: rvar
  character*80 :: line
  
  write(*,*) "Reading file..."

  ! open input file
  open(10,file='DATA-002.csv',status='old',iostat=stat)
  if (stat .ne. 0) then
    write(*,*) 'File cannot be opened !'
    go to 99   
  end if

  num_lines = 0
  do
    read(10,'(A)',end=99, iostat=stat) line 
    if (stat .ne. 0) then
      write(*,*) 'Error reading data !'
      go to 99
    end if
    ! skip comment/header lines beginning with ";"
    if (adjustl(trim(line(1:1))) .eq. ';') then
      cycle
    end if
    ! read string line into numeric variables
    read(line,*) rvar, ivar1, ivar2, ivar3
    num_lines = num_lines + 1    
    if (num_lines <=  10) then
      write(*,*) num_lines, ':', rvar, ivar1, ivar2, ivar3
    end if
  Sum_ivar1 = Sum_ivar1 + ABS(ivar1) 
  Sum_ivar2 = Sum_ivar2 + ABS(ivar2) 
  Sum_ivar3 = Sum_ivar3 + ABS(ivar3)
  Max
  end do

  ! close file
  99 continue
  Avg_ivar1 = (Sum_ivar1 / num_lines)
  Avg_ivar2 = (Sum_ivar2 / num_lines)
  Avg_ivar3 = (Sum_ivar3 / num_lines)
  close (10)
  !
  write(*,*) '...done.'
  write(*,*) 'Lines processed: ', num_lines
  write(*,*) 'Average vertical acceleration', Avg_ivar1/1000
  write(*,*) 'Average sideways acceleration', Avg_ivar2/1000
  write(*,*) 'Average forwards acceleration', Avg_ivar3/1000
end program WSUPhys_csv