Shell Programming and Scripting

I have a text file in the following format
....
START
1,1
2,1
3,1
..
..
9,1
10,1
END
....

I want to change to the output to
....
START
1,1
2,1
3,1
..
..
9,1
10,1
11,1
..
..
99,1
100,1
END
.....

With my little knowledge of sed I could come this far.
sed '/START/,/END/' provides a means of addressing the range. But how to add consecutive numbers from 11 to 99 before END???

Btw the file is filled with numbers before START and after END.

Thanks in advance
VNR

Code:

awk '/END/{for(i=11;i<101;i++){print i",1"}}{print}' file

Regards

works like a charm....thanks very much for the fast reply

Code:

i=10
while [ $i -lt 101 ]
do
        echo ${i},1 >> filename
        i=`expr $i + 1`
done

The above code only appends the numbers at the end of filename. I wanted to add the numbers only before END. As I mentioned there are numbers before and after START and END.