minimize icon to the vba form and remove close icon.

To disable both the close button and close menu option from the system menu on a VB form, use this

visual basic code:Option Explicit

Private Const xSC_CLOSE As Long = -10
Private Const SC_CLOSE As Long = &HF060&
Private Const MIIM_STATE As Long = &H1&
Private Const MIIM_ID As Long = &H2&
Private Const MFS_GRAYED As Long = &H3&
Private Const WM_NCACTIVATE As Long = &H86

Private Type MENUITEMINFO
    cbSize As Long
    fMask As Long
    fType As Long
    fState As Long
    wID As Long
    hSubMenu As Long
    hbmpChecked As Long
    hbmpUnchecked As Long
    dwItemData As Long
    dwTypeData As String
    cch As Long
End Type

Private Declare Function GetSystemMenu Lib "user32" ( _
    ByVal hWnd As Long, ByVal bRevert As Long) As Long

Private Declare Function GetMenuItemInfo Lib "user32" Alias _
    "GetMenuItemInfoA" (ByVal hMenu As Long, ByVal un As Long, _
    ByVal b As Boolean, lpMenuItemInfo As MENUITEMINFO) As Long

Private Declare Function SetMenuItemInfo Lib "user32" Alias _
    "SetMenuItemInfoA" (ByVal hMenu As Long, ByVal un As Long, _
    ByVal bool As Boolean, lpcMenuItemInfo As MENUITEMINFO) As Long

Private Declare Function SendMessage Lib "user32" Alias _
    "SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, _
    ByVal wParam As Long, lParam As Any) As Long

Private Declare Function IsWindow Lib "user32" _
    (ByVal hWnd As Long) As Long


Private Function EnableCloseButton(ByVal plnghWnd As Long, pblnEnable As Boolean) As Integer
         Dim lngMenuID As Long
    EnableCloseButton = -1
    If IsWindow(plnghWnd) = 0 Then Exit Function
    Dim hMenu As Long
    hMenu = GetSystemMenu(plnghWnd, 0)
   
    Dim MII As MENUITEMINFO
    MII.cbSize = Len(MII)
    MII.dwTypeData = String(80, 0)
    MII.cch = Len(MII.dwTypeData)
    MII.fMask = MIIM_STATE
   
    If pblnEnable Then
        MII.wID = xSC_CLOSE
    Else
        MII.wID = SC_CLOSE
    End If
        EnableCloseButton = -0
    If GetMenuItemInfo(hMenu, MII.wID, False, MII) = 0 Then Exit Function
        lngMenuID = MII.wID
   
    If pblnEnable Then
        MII.wID = SC_CLOSE
    Else
        MII.wID = xSC_CLOSE
    End If
        MII.fMask = MIIM_ID
    EnableCloseButton = -2
    If SetMenuItemInfo(hMenu, lngMenuID, False, MII) = 0 Then Exit Function
        If pblnEnable Then
        MII.fState = (MII.fState Or MFS_GRAYED)
        MII.fState = MII.fState - MFS_GRAYED
    Else
        MII.fState = (MII.fState Or MFS_GRAYED)
    End If
        MII.fMask = MIIM_STATE
    EnableCloseButton = -3
    If SetMenuItemInfo(hMenu, MII.wID, False, MII) = 0 Then Exit Function
    SendMessage plnghWnd, WM_NCACTIVATE, True, 0
    EnableCloseButton = 0
End Function

Private Sub Form_Load()
EnableCloseButton Me.hWnd, False
End Sub