Collecting several digital signatures without locking the spreadsheet

Hello everyone.

I'm having a very specific problem at the company I'm working at. I am responsible for the planning and execution of several projects and, in order for these projects to be accepted by the "program", I have to collect signatures from all the departments that are impacted on the project.

Right away, I face several problems. I can list them:

• Sometimes, the person wants to add observations on the sheet, like: I am only favorable if X happens at the Y week. And after the first person signs it, the next one cannot put these observations in a VISIBLE spot (these observations influence other people's signature, they can't be just inside the signature, they must be very visible);
• There are some problems sending the spreadsheet: it must be done using outlook, therefore, the person should be able to sign the spreadsheet, save it, send it back to be so I can send to the next person (there is a sequence to be followed);
• There must be a way to certify and secure whoever is signing. The default signature line from Excel works perfectly regarding this matter: it automatically puts the e-mail of the person who signed it (digital certificate) just below the signature. The quality department will not accept any level of security below this: the signature must be linked with the digital certificate of the person.

I was wondering if I could pull the certificate of the person using the spreadsheet when the person signs where he or she is supposed to sign, using VBA, and still do NOT lock the spreadsheet (just some cells).

I am attaching an example spreadsheet that is just like the spreadsheet I manage (blank, of course).

The perfect scenario: the Excel's default signature lines without locking the entire spreadsheet after the first signature.

Thanks in advance for the help...