Attached is a CueCat Software written in Tcl.  Since most system have Tcl available I thought this was a good solution (  Also a program can be written with this package to bind to the ALT-F10 keystroke that preceeds the CueCat decode string (Note: the ENTER ends the cuecat string).  This software is under a open source license (same as Tcl).
This Package needs to be source into a Tclsh or Wish console or your own Tcl script. 
The command are
    CueCat::Decode "Scan the item or just past the results"
    CueCat::Encode "Takes the string and does a encodeing .. I use this to verify my Decoder"
    CueCat::ISBN "takes the output of Decode and finds the ISBN number"
example done in Tclsh
% source cuecat.tcl
% CueCat::Decode .C3nZC3nZC3nZCxj2Dhz1C3nX.fHmc.DxPYE3b6C3nZC3jY.
000000000215756002 UPA 691839000011
% CueCat::Encode [CueCat::Decode .C3nZC3nZC3nZCxj2Dhz1C3nX.fHmc.DxPYE3b6C3nZC3jY.]
% CueCat::ISBN [CueCat::Decode .C3nZC3nZC3nZCxj2Dhz1C3nX.fHmc.DxPYE3b6C3nZC3jY.]
**Note I know that a UPA is not a IB5 scan but it was handy for this example