Newbee and loads of doubts please see

there is scroller attached for which i am using this i am also attaching the schematic design of the circuit
please help

this is the basic program i am using to get the leds glow with the moment of the scroller
the input is more like shown below ( has a small phase difference

pin2 ==> |-|
pin4 ==> |-|

but using this program i am able to capture the the changes and the leds glows
like if i hav led A and led B
so if i have the above input the pins will glow like
like A first and B
and then A and B both r ON
and then just B is ON
what i want is
for the above input that if i get pin2 i want to ignore pin4 and in case the input is lik ethis one
pin2 ==> |-|
pin4 ==> |-|
i want to ignore the pin2
and i want to use the counter in the program to count the number of inputs that i am getting from the scroller
please help me put

#include <avr/io.h> 

int main() 
{ 
   uint8_t i; 

   PORTB= 0x00; 

/* PB0, PB1 & PB3 are outputs; PB2 & PB4 are scroller inputs */ 
   DDRB = (1<<PB3) | (1<<PB1) | (1<<PB0); 

   PORTB = 0; 

   for(;;) { 
      i = PINB; 

      if ( (i & (1<<PB2)) != 0) { 
         PORTB |= (1<<PB0); 
      } 
      else { 
         PORTB &= ~(1<<PB0); 
      } 

      if ( (i & (1<<PB4)) != 0) { 
         PORTB |= (1<<PB1); 
      } 
      else { 
         PORTB &= ~(1<<PB1); 
      } 
      _delay_us(100); /* wait for a while */ 

   } 
}

in my mind i had more like a truth table to work on but not able to impliment it
like the input is more like
up ==> 001100
down=> 000110
and in this case i want to ignore the input at the down and send only one out put

pin2 ==> |-|
pin4 ==> |-| for upward moment
if this is the input more like
01100
00110

pin2 ==> |-|
pin4 ==> |-| for downward moment
if this is the input more like
00110
01100

i just want to capture the change in the bit at the signal
and which ever changes first i want to pick that one and niglect the other one

it was suggested by Cliff to use ISR
but i am not able to understand how to intiate this interrupt
if someone can help please