have a while loop that runs while a is not pressed
WHILE BUTTON()!=#A
put in some code to check whether left dpad button is pressed, if so, move the selection left
IF BUTTON(3) == #LEFT THEN DEC SEL
vice-versa with right dpad button
IF BUTTON(3) == #RIGHT THEN INC SEL
now limit the selection variable
IF SEL < [lowest number] THEN SEL = [lowest number]
-cont-
-cont- do not include the -cont-s in your code
IF SEL > [highest number] THEN SEL = [highest number]
now figure out a way to show the selection, this shouldn't be hard
[your code here]
end the while loop
WEND
and no, i won't help you much with the showing selection code.