code to automating digital sign

Hello!
I would like to make a program to digital sign a lot of created excel with
macros.

I only find there example, but is not enough:

Public Function IsWordProjectSigned(strDocPath As String) As Boolean
Dim docProj As Word.Document

' Open document.
Set docProj = Documents.Open(strDocPath)

' Check VBASigned property of document.
If docProj.VBASigned Then
IsWordProjectSigned = True
Else
IsWordProjectSigned = False
End If
End Function


Every one can help me??
Thaks a lot and sorry my poor english.