Help with error message (2003 sp2)

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I cannot understand why I get the error message “invalid uses of Null” in this procedure at the first line beginning “IF Left(Me…”. It worked fine when I first tested it and now it does not.

The intention is to test for a 12/25 or 7/4 (any year) date and if true make a button on the form visible.

Private Sub Combo17_AfterUpdate()
‘ Find the record that matches the control.
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst “[ASSET_NUMBER] = ‘” & Me![Combo17] & “‘”
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
If Left(Me.INSPECT_DATE, Len(Me.INSPECT_DATE) – 5) = “07/04” Then
Me.cmd_ARC1.Visible = True
End If
If Left(Me.APPRAISE_DATE, Len(Me.APPRAISE_DATE) – 5) = “12/25” Then
Me.cmd_ARC2.Visible = True
End If
End Sub

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If the control INSPECT_DATE is blank you’d get this error message, so you should check for that before the If statement, e.g.

If IsNull(Me.INSPECT_DATE) Then
MsgBox “Please enter a date!”, vbExclamation
Me.INSPECT_DATE.SetFocus
Exit Sub
End If

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Why don’t I think of these things? However, null is valid for the Inspect_Date field if an inspection has never been done. I know, we never seem to give enough information.

I changed the line to If Left(Me.INSPECT_DATE, 5) = “07/04” Then and I do not get any errors.

I can’t help wondering why it works when it essentially says the same thing.

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Left(Null, 5) returns Null, and Null doesn’t equal “07/04”, so that works as intended.

Len(Null) is not 0 but Null, so Left(Null, Len(Null)-5) evaluates to Left(Null, Null) and VBA can’t handle this.

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Now I see said the blind man.

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