IF...THEN inside a Loop

[sayzer]

What happens if X=1 ?

Also,
IF X<1 THEN PORTB=$F0 is the same as X = 0

IF X>1 AND X<3 THEN PORTB=$3C is the same as X = 2

IF X>2 THEN PORTB=$0F is the same as X = 3 ( For loop goes to 3)

Thus,

IF X = 0 THEN PORTB=$F0
IF X = 2 THEN PORTB=$3C
IF X = 3 THEN PORTB=$0F

looks better.