Customer exit to populate string against KF in BEx query

Hi Experts,

I have a reporting requirement where based upon the value of a KF I wish to display a string in the corresponding column. For example if value is between 0 to 50, display string "AVG", if greater than 50 and less than 90, display "Good" and if greater than 90, display "Excellent".

Wherein BO WEBI reports it is easily achievable, is there any way to achieve this in Bex maybe through customer exit? Only other option I am aware is using conditional formatting.

Regards