How to use many signatures on an excel document that needs to be shared and signed.

for example i am working on an excel workbook. This needs to be signed by everyone in my department before I send it to the vendor. I insert three different signatures, that need to be signed by two other people. Mary, Rick, and myself. I sign my name first. then it becomes a read only copy. Although I want to share it with Mary, and Rick. so they too can sign off on it. When I share it with them, they get the message that the file is read only, even if they try to sign it - they get a message that the file is already signed. Cannot be edited. Is there a way to get this file shared and then signed on by the people I have inserted the signature file. It becomes read-only when I sign it. I can sign all three different signatures in my pc. Like I sign my name, then it becomes an only-read file, but I can still sign Mary and Rick names.