Here's a API function the Disables the Close button. 2

[MrVB50au]

The following disables the close button on a MDIForm but can be used for any other form as well.

Option Explicit

Const MF_BYPOSITION = &H400

Private Declare Function GetSystemMenu Lib "User32" (ByVal hWnd As Long, ByVal bRevert As Long) As Long
Private Declare Function RemoveMenu Lib "User32" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long

Private Sub MDIForm_Load()
RemoveMenu GetSystemMenu(Me.hWnd, 0), 6, MF_BYPOSITION
End Sub

 

[SkennyR]

Thats a very useful post, and it works great!!
A star for you!

 

[gavinhuet]

Just a small note to remember about doing this:
just because the close menu is disabled does not mean that a user cannot close the form down without clicking on some special button or link.
If you press ALT+F4 the form will still close down, you will need to trap for this in the form KeyDown event.

Gavin