Something like this should work.
Code:
program:
## obviously replace $#yournum with your column
if
$#yournum>=#10000000
&&
$#yournum<=#10999999
then
## using 'round' to fix the float/decimal output I got in my test
round(subtract($#yournum, 100000000))
else
$#yournum
fi
You'll want the "else $#yournum" or it will give you a blank for those instances.