Crystal Reports blob field or memo feild cannot be used in a formu

Message

   I am getting an error : 
blob field or memo feild cannot be used in a formula  when I use the following formula...I am using CR 8.5 and oracle 10g as the backend. 

help appreciated.

if {Query.SOURCE}='PD'
 then iif(ucase(left({Query.BATCHDESC},6))='FISCAL',val(mid({Query.BATCHDESC},8,4)),{Query.CURRENT_YR})
else
 if {Query.SOURCE}='AL'
  then val({Query.CFISCAL_YR_END})
else
 if isnull({Query.MISC_REFERENCE}) or ucase(left({Query.MISC_REFERENCE},6))<>'FISCAL'
   then {Query.NFISCAL_YR_END}   
 else
  val(mid({Query.MISC_REFERENCE},8,4))