Access CloseButton

Hi

I've tried using the following code to disable the close button on form open:

Private Sub Form_Open(Cancel As Integer)

Me.CloseButton = False

End Sub

But I get the following error when opening the form:

Run-time error '2448':

You can't assign a value to this object.

I don't understand why you can't assign a value as the VB Editor offers you True/False as a value after you've typed the equals sign.

Thanks

David