Hot to manipulate Bex Query Output

Dear Expert,

I am running a report where there are 2 KF say X & Y

Now when KF X is showing some data Y is also displaying data based on that

But when KF X is showing 0 value,Y is displaying value as "X"

Now my requirement is when KF X is shwoing as 0 values Y should display fix values as "9999"

How wil achieve this ?

Thanks,

Neetu