こんな感じ？意図が違ったらごめん。
unsigned char psw = 0xFF;
unsigned char mode = 0;

void main(void)
{
init();

while (1) {
delay_ms(10);

psw = psw << 1;
if ( IO_RB4_PORT ) {
psw = ( psw | 0x01 ) & 0x0F;
}else{
psw = ( psw & 0xFE ) & 0x0F;
}
if ( psw == 0x0C ) {
mode++;
if ( mode >= 4 ) {
mode = 0;
}
}

switch ( mode ) {
case 0:
IO_RA3_LAT = 1;
IO_RA4_LAT = 1;
break;
case 1:
IO_RA3_LAT = 1;
IO_RA4_LAT = 0;
break;
case 2:
IO_RA3_LAT = 0;
IO_RA4_LAT = 0;
break;
case 3:
IO_RA3_LAT = 1;
IO_RA4_LAT = 0;
break;
}
}
}