It is impossible inside the loop, even in F77.

But if a global variable is used as a loop counter, and the variable is altered in a subroutine, then the code altering the variable is not inside the loop. At least not in the eyes of the Fortran compiler.

    $ cat test.f08

    program test
        integer i
        do i = 1,3
            call sub
            print *,i
        end do
    contains
        subroutine sub
            i = 3
        end subroutine sub
    end program test

    $ gfortran --std=f2008 test.f08 
    $ ./a.out 
           3