Public Declare Function RemoveMenu Lib "user32.dll" ( _
ByVal hMenu As Int32, _
ByVal nPosition As Int32, _
ByVal wFlags As Int32) As Int32
 
bzw.
 
RemoveMenu(GetSystemMenu(Me.Handle.ToInt32, 0), SC_CLOSE, MF_BYCOMMAND)

Public Declare Function InsertMenu Lib "user32.dll" Alias "InsertMenuA" ( _
ByVal hMenu As Int32, _
ByVal nPosition As Int32, _
ByVal wFlags As Int32, _
ByVal wIDNewItem As Int32, _
ByVal lpNewItem As Int32) As Int32
 
bzw.
 
InsertMenu(GetSystemMenu(Me.Handle.ToInt32, 0),SC_CLOSE,MF_BYCOMMAND,?1?,?2?)