I can imagine how it may be done in ASM language; it seems you try to build sheduler for time-quanta based tasks...
Well, in C-language it is not so clean. Anyway, maybe:
1) Just call routine 2 inside timer ISR? someting like:

void timer_isr(void) interrupt 1 using 1 
{ 
routine2();
}

2) Set a signal for routine 1 that it should be holded, like:

void timer_isr(void) interrupt 1 using 1 
{ 
task2_time = 1;
}

routine1()
{
while(1)
{
  if (task2_time)
  {
    routine2();
    task2_time = 0;
  }
}
}

good days!