getting Selection.OnAction to recognize correct workbook

I have a routine that reduces a large monthly data set, then parses the data into individual workbooks (each month on a separate tab) for a number of different departments. The workbooks are stored online in a common directory for each department to access and update.

In order to improve things, management wants each department to certify they have reviewed and updated the data. I've programmed a form button (as opposed to an activex button) that the user can click when they have completed their data which will send me an e-mail certification.

I've put the e-mail code into the "ThisWorkbook" sheet of each department's workbook. The expectation is that the pointer to the e-mail code will be to the local copy in each department's workbook when the

Selection.OnAction

command is generated for each month in each workbook.

The code works as advertised except that the command "

Selection.OnAction

= "ThisWorkbook.CertifyEmail" always tries to reference my source code, not the local department copy” (On my machine, my source code opens and runs the e-mail routine without issue - obviously I can't have my users accessing my master file)

Here’s the code that generates the button on each month’s worksheet within each department’s file:

Sub UpdateConfirmation()

 Dim x As String
 
    ActiveSheet.Buttons.Add(99.6, 51, 150, 70).Select
    x = Selection.name
    
    ' e-mail generation routine
    Selection.OnAction = "ThisWorkbook.CertifyEmail"
    
    ActiveSheet.Shapes(x).Select
    Selection.Characters.Text = _
        "Click this button to confirm you have updated " & _
        "this month's data with current information " & _
        "(an e-mail will be sent automatically)"
       
End Sub

Any suggestions how to get the OnAction command to reference the local code in each department's workbook?

Art