[CentOS] sed question

I am trying to use sed to change a value in a pipe.

------------------- This is the two line script
CHANGE="1234"

cat my_file.txt | sed 's/CANCELID/$CHANGE/' > cancel.txt
-------------------

and the my_file.txt has:
         <v1:notificationId>CANCELID</v1:notificationId>

it gets changed to $CHANGE instead of the actual value 1234 .
I tried putting a \ in front of the $ also and made no difference.

What am I not doing correctly.

Thanks,

jerry