Hello @Suresh ,
Welcome to Q&A Forum!
According to my research, we could not set conditional formatting for SUM function, it is by design.
This is because SUM is only a sum() function that works on Number column and Currency column, not a field.
Thanks,
Echo Du
==============================
If an Answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.