Can you create a custom signature format to include a character in the signature?

Is there a way to create a custom signature so that it always includes certain characters in the signature field?  For example, can the signature field be formatted such that the typed signature appears between two forward slashes.  So when a signer signs, the signature is "/first last/"?  I can always instruct the signer to manually insert these slashes in the mssage, but if they forget or miss the message, then the document must be re-signed (inconveniencing other who have signed correctly).  Any suggestions?