こういうの?
dim sel[3],sel$[3]
for i=0 to 2
read sel[i]
locate 10,sel[i]:? sel$[i]
next
data 5,"new game",8,"continue",data 11,"end"
while 1 '---------------------------ここから下が重要
locate 8,sel[y]:? " "
b=button(2)
y=y+!(b and #up)*(y<0)-!(b and #down)*(y>2)
locate 8,sel[y]:? ">"
if b and #a then ret=y:break
vsync
wend
多分動く