void Init_Timer1(void)
{
	TCCR1A = 0x00;
	TCCR1B = _BV(CS11) | _BV(WGM12);  // clk/8 and normal count up
	TCCR1C = 0x00;
	OCR1A = TIMERTICKS;
	TIMSK1 = _BV(OCIE1A);  //enable compareA ISR
}

and

ISR(TIMER1_COMPA_vect)
{
	TGL_LEDY();
}

With this in the main loop somewhere:

main(void)
{
 	Init_Timer1();
	foo...
	sei(); //init global irqs.
	bar...
}