type t_command is (stop, run, hold, priority_grant);
signal s_command           : t_command                            := stop;

user_cmd_req_gnt_p: process
variable v_tb_cnt : integer      := 0;
begin
   signal_force("/top_tb/tb_control_array(" & to_str(v_tb_cnt) & ").command", "hold", 0 ns, freeze, open);
   while (true) loop
      init_signal_spy("/top_tb/tb_control_array(" & to_str(v_tb_cnt) & ").command", "s_command", 1);
      wait for 1 ps;
      if (s_command = stop) then
         exit;
      else
         v_tb_cnt          := v_tb_cnt +1;
         signal_force("/top_tb/tb_control_array(" & to_str(v_tb_cnt) & ").command", "hold", 0 ns, freeze, open);
         s_command         <= stop;
      end if; 
      -- wait for 1 ps;
   end loop;
   wait for 1 ps;
   for i in 0 to v_tb_cnt-1 loop
      signal_force("/top_tb/tb_control_array(" & to_str(i) & ").command", "stop", 0 ns, freeze, open);           -- force test level sdias
   end loop;
   ...
end process user_cmd_req_gnt_p;