Help ! Cryption rcc compiling error

CryptionRCC error LNK2019: unresolved external symbol "void __cdecl CCrypt::Decryption(unsigned char *,int)" (?Decryption@CCrypt@@YAXPAEH@Z) referenced in function "public: int __thiscall CCryptionRCCDlg::FileDecryption(class ATL::CStringT<char,class StrTraitMFC_DLL<char,class ATL::ChTraitsCRT<char> > >,class ATL::CStringT<char,class StrTraitMFC_DLL<char,class ATL::ChTraitsCRT<char> > >)" (?FileDecryption@CCryptionRCCDlg@@QAEHV?$CStringT@DV?$StrTraitMFC_DLL@DV?$ChTraitsCRT@D@ATL@@@@@ATL@@0@Z)

i encount this error on visual studio 2003
please help me solve this error.
Thanks in advance.