scrolling text field

[Preston Shea]

I'm trying to get text to scroll up from the bottom (like movie credits) with a
handler:

set the scroll of fld "credits" to 0
# (scroll of fld "credits" = 1450
  repeat with n = 1 to 1450
set the scroll of fld "credits" to n
end repeat

The script seems to run fine the first time but then although the field scrolls,
the text fails to display and the field shows empty. The field uses a balck
background and a white foreground. What am I doing wrong?