I have a spreadsheet used as a database. Upon open or activation I want to
show the dataform automatically. Upon close or deactivation of the worksheet
I want it to close automatically.

My code on closing or deactivation doesn't work. You have to physically
select the close button on the form or use Alt-L for the keyboard shortcut.
Apparently the open form precludes the macros.

Can I close the form automatically and, if so, how?

My code (in ThisWorkbook)

Private Sub Workbook_BeforeClose(Cancel As Boolean)
On Error Resume Next
SendKeys "%{L}", True
End Sub

Private Sub Workbook_Open()
On Error Resume Next
ActiveSheet.ShowDataForm
End Sub

Private Sub Workbook_WindowActivate(ByVal Wn As Window)
On Error Resume Next
ActiveSheet.ShowDataForm
End Sub

Private Sub Workbook_WindowDeactivate(ByVal Wn As Window)
On Error Resume Next
SendKeys "%{L}", True
End Sub