Well if you want it like Pokemon then it's not really scrolling but rather just hitting the next line of strings.
Use an array to store your strings.
sync on
Pos as float
dim Dialog$(10)
Dialog$(0) = "Hi what can I do for you?"
Dialog$(1) = "So you want to buy a Pokemon?"
Dialog$(2) = "I'm sorry but they cannot be sold."
Dialog$(3) = "If you want one then you have to catch it."
Dialog$(4) = "What don't have a Pokeball?"
Dialog$(5) = "Then scram! We only sell bikes here!"
ink rgb(255,255,255),0
do
gosub PlayDialog
sync
cls
loop
PlayDialog:
text 100,100,left$(Dialog$(D),Pos)
if Pos < len(Dialog$(D)) then inc Pos,.01
if Pos => len(Dialog$(D))
if spacekey()
Pos = 0
inc D
if D = 6 then end
endif
endif
return