Applescript iWork error

I have just started working with applescript instead of automator. I tried to make a program which added a column in a spreadsheet after a, then filled the top ten rows of that collumn with the word name. Why does the following code not work?:

set thisCSVFile to choose file

if (thisCSVFile as string) ends with ".csv" then

tell application "Numbers"

open thisCSVFile

tell front document

tell table 1 of sheet 1

add column after column "A"

repeat with a from 1 to 10

set value of cell a of column "B" to "name"

end repeat

end tell

end tell

end tell