Force-quit when external xlsm libraries are referenced and open - vba

Question

I have three files, one is app.xlsm, the other one is lib.xlsm, whereas app.xlsm uses lib.xlsm as a reference (which is specified in Tools -> References). The third, third.xlsm has the following code:
Private Sub Workbook_Open()
prompt = MsgBox("If you click Ok, Excel will force close." & vbCrLf & _
"If you click Cancel, you can work with the file", vbOKCancel)
If prompt = vbOK Then
Application.DisplayAlerts = False
thisworkbook.Close True
Application.Quit
End If
End Sub
Assume that I have app and lib open. Now when I open third, and then click OK at the prompt, app gets closed but lib remains open. I.e. Excel does not get force shut.
I need Excel to close all files without saving them and close silently.
Many thanks.

Answer 1

What happens if you loop through the open workbooks in this instance, ie
Private Sub Workbook_Open()
Dim wb As Workbook
prompt = MsgBox("If you click Ok, Excel will force close." & vbCrLf & _
"If you click Cancel, you can work with the file", vbOKCancel)
If prompt = vbOK Then
For Each wb In Application.Workbooks
If wb.Name <> ThisWorkbook.Name Then wb.Close False
Next
End If
ThisWorkbook.Saved = True
Application.Quit
End Sub
thermonuclear option to close all Excel instances
Private Sub Workbook_Open()
Dim wb As Workbook
prompt = MsgBox("If you click Ok, Excel will force close." & vbCrLf & _
"If you click Cancel, you can work with the file", vbOKCancel)
If prompt = vbOK Then
For Each wb In Application.Workbooks
If wb.Name <> ThisWorkbook.Name Then wb.Close False
Next
End If
X2 = Shell("powershell.exe kill -processname excel", 1)
End Sub