Onkey gone haywire!!!

Hi,

I am using the following macros and they work fine if I attach it to the f9 key or run them from the vb editor but if I attach it to the shift f9 key the macro stops after it opens the file????? This makes no sense to me!! Any help greatly appreciated

Public Sub Workbook_Open()

Application.OnKey key:="+{F9}", procedure:="RecalcShftF91"

End Sub

Public Sub RecalcShftF91() 'this occurs if they use Shift F9


' Checks whether a file exists

Dim fso
Dim file As String

file = "\\Testing.txt" ' '  file & w/Path
Set fso = CreateObject("Scripting.FileSystemObject")


' Does the file exist?


If Not fso.FileExists(file) Then
    
GoTo Line1 'If the file doesn't exist

Else 'if the file does exist
 
Workbooks.OpenText Filename:="\\Testing.txt"
     

ActiveWorkbook.Close


End If
    
Line1:


End Sub