DelMinMaxBtn

Sub MDIForm_Load()
Dim lWnd as Long
lWnd = GetWindowLong(Me.hWnd, GWL_STYLE)
lWnd = lWnd And Not (WS_MINIMIZEBOX)
lWnd = lWnd And Not (WS_MAXIMIZEBOX)
lWnd = SetWindowLong(Me.hWnd, GWL_STYLE, lWnd)
End Sub

'Add this code (which includes the required API declarations) to a BAS module:

#If Win32 Then
Private Declare Function SetWindowLong Lib "user32" _
Alias "SetWindowLongA" (ByVal hwnd As Long, ByVal _
nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function GetWindowLong Lib "user32" _
Alias "GetWindowLongA" (ByVal hwnd As Long, ByVal _
nIndex As Long) As Long
#Else
Declare Function SetWindowLong Lib "User" (ByVal hwnd _
As Integer, ByVal nIndex As Integer, ByVal _
dwNewLong As Long) As Long
Declare Function GetWindowLong Lib "User" (ByVal hwnd _
As Integer, ByVal nIndex As Integer) As Long
#End If
Const WS_MINIMIZEBOX = &H20000
Const WS_MAXIMIZEBOX = &H10000
Const GWL_STYLE = (-16)
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Unlike other forms, MDI forms don't have MinButton and
MaxButton properties enable or disable the form's Minimize
and Maximize buttons. If you add this code to an MDI
parent form's Load event, it disables the Minimize and
Maximize buttons on the MDI form. If you just want to disable
one or the other, comment out the appropriate line,
based on which constant you don't need: