Add Digital Signature For Macros

I'm trying to apply the digital signature automatically to excel files(.xls,.xlt)(from Excel VBA editor-->Tools-->digital signature--->Apply signature(i need to apply this settings through code)).

scenarios:

1. I could apply digital signature for .exe,.dll,.cab files through VB6 code(using capicom dll) and also i can achieve this to Word document by using signature object.But this object not supporting in Excel.

2. I tried also like this, Recrod a macro--->Apply digital signature from VBA Editor (tools-->digital Signature) but no code has been generated.Again i tried this in another way like, Record macro-->Tools(from Excel)-->Options-->Security-->Digital Signatures--->Add.but here also i couldn't achieve this.

3. i tried using Application object like executing menus through code(Application. commandbars("Tools").controls("Options").controls("security")) here also i strucked up.

I've verisign digital certificate with pfx file.....