Thank you ALL for your ideas and reply.
As Brian said, if we use (1/0) expression, its always giving 'X'. I tested by using the below statement for confirmation.
Formula1: (kf == 999999)*(1/0) + 1
Formula2: (kf <> 999999)*(1/0) + 1
In both the cases the result is showing as X only. Hence this 1/0 logic may not work for my scenario.
Hope my requirement is clear. I committed to user that if KF is 999999 then will display that KPI No value as X . Unfortunately, unable to stand on my word 
. Could some one suggest any other alternative how can we achieve this requirement.
Best Regards
Venkat...