mANO,
Crystal Reports will throw this error if it believes it is working with a value that is not a number. Crystal has many conversion functions like (CDBL, CSTR, etc) and also data check functions (IsNull, IsNumeric, etc) that you can use.
In your particular case, converting the values to a DBL (CDBL({field}) solves your problem after Crystal checks for null values or blanks.
Due to converion problems are occured
Thanks,
DJ
