need help with gawk script

hi i've already created this script. When I execute the script it takes the argument and compares it to the 3rd column of the script. What I was wondering if I could get some help with is. I want to add another column to the script and it will be the result of a set number for example, (2000 - 3rd column)/4th column.

cat file
text     text      600     80      text

while read line
do
let arg=$1
gawk '{{
        if ($3 < '$arg')  printf  "*%-10s %-8s   %2d   %5d    $ %8.2f\n", $1, $2, $3, $4, $5;
else
 printf "%-10s %-8s   %2d   %5d    $ %8.2f\n", $1, $2, $3, $4, $5 }}'

done < file

I am looking for the result to come out like

text     text      600     80      text     (Result of (2000-600)/80)

It might be something like this but I was having trouble in writing a code to work in the printf field.

while read line
do
let arg=$1
let set=2000

gawk '{{
        if ($3 < '$arg')  printf  "*%-10s %-8s   %2d   %5d    $ %8.2f\n", $1, $2, $3, $4, $5, $6;
else
 printf "%-10s %-8s   %2d   %5d    $ %8.2f\n", $1, $2, $3, $4, $5 }}'

done < file

thanks for the help

----------

awk -v set="2000" '{printf("%s%8.2f\n", $0, (set-$3)/$4)}' file

thanks I kinda figured it out, it wasn't the perfect way but it worked. heres the code in case anyone needs it in the future.

let arg=$1
gawk < file '{{
        if ($3 <= '$arg')
{
set=2010
avg=($4/(set-$3))

printf "*%-10s %-8s   %2d   %5d    $ %8.2f", $1, $2, $3, $4, $5, $6
print  "  "avg
}
 else
 {
set=2010
avg=($4/(set-$3))

 printf "%-10s %-8s   %2d   %5d    $ %8.2f", $1, $2, $3, $4, $5, $6
print  "  "avg
}}

}'

I probably would like to make it look cleaner if anyone knew how to put the avg into the printf fields. Thank you guys