Why this script doesn't work ?

The script:

tell application "Finder"
activate
repeat
set w to display dialog "salary?" default answer "2000"
set wSal to text returned of w
display dialog wSal
--processing of wSal
end repeat
end tell

When running this script on my computer it's impossible to change the
value (2000) inside the display dialog window; why?

Thanks in advance

Pierre