start-of-selection

    lv_max_lines = class1->get_max_lines( ).

    do lv_max_lines.
        class2->method1( class1->get_line_by_index( sy-index ) ).
    enddo.


class 2 implementation.

    method method1.
        method2( is_line ).
    endmethod.

    method method2.
        method3( is_line ).
    endmethod.

    method method3.
        if ls_line <> what_I_need.
            class1->reject( ). "or
            class1->reject( is_line ).
            "go back straight to start of selection and execute next iteration,
            "ignoring the rest of method3 and metho2 and method1 from class2.
        endif.
        "more process
    endmethod.

endclass.