Isso fará isso:
Sub getafile()
Dim fStr As String
With Application.FileDialog(msoFileDialogFilePicker)
.Show
If .SelectedItems.Count = 0 Then
MsgBox "Cancel Selected"
End
End If
'fStr is the file path and name of the file you selected.
fStr = .SelectedItems(1)
End With
'Replace with your code.
MsgBox fStr
End Sub