Declarations

Code:
'Declare a user-defined variable to pass to the Shell_NotifyIcon
'function.
Private Type NOTIFYICONDATA
    cbSize As Long
    hWnd As Long
    uId As Long
    uFlags As Long
    uCallBackMessage As Long
    hIcon As Long
    szTip As String * 64
End Type

'Declare the constants for the API function. These constants can be
'found in the header file Shellapi.h.

'The following constants are the messages sent to the
'Shell_NotifyIcon function to add, modify, or delete an icon from the
'taskbar status area.
Private Const NIM_ADD = &H0
Private Const NIM_MODIFY = &H1
Private Const NIM_DELETE = &H2

'The following constant is the message sent when a mouse event occurs
'within the rectangular boundaries of the icon in the taskbar status
'area.
Private Const WM_MOUSEMOVE = &H200

'The following constants are the flags that indicate the valid
'members of the NOTIFYICONDATA data type.
Private Const NIF_MESSAGE = &H1
Private Const NIF_ICON = &H2
Private Const NIF_TIP = &H4

'The following constants are used to determine the mouse input on the
'the icon in the taskbar status area.

'Left-click constants.
Private Const WM_LBUTTONDBLCLK = &H203   'Double-click
Private Const WM_LBUTTONDOWN = &H201     'Button down
Private Const WM_LBUTTONUP = &H202       'Button up

'Right-click constants.
Private Const WM_RBUTTONDBLCLK = &H206   'Double-click
Private Const WM_RBUTTONDOWN = &H204     'Button down
Private Const WM_RBUTTONUP = &H205       'Button up

'Declare the API function call.
Private Declare Function Shell_NotifyIcon Lib "shell32" Alias "Shell_NotifyIconA" (ByVal dwMessage As Long, pnid As NOTIFYICONDATA) As Boolean

'Dimension a variable as the user-defined data type.
Dim nid As NOTIFYICONDATA



in form_load

Code:
    nid.cbSize = Len(nid)
    nid.hWnd = frmChanger.hWnd
    nid.uId = vbNull
    nid.uFlags = NIF_ICON Or NIF_TIP Or NIF_MESSAGE
    nid.uCallBackMessage = WM_MOUSEMOVE
    nid.hIcon = frmChanger.Icon
    nid.szTip = "Background Changer" & vbNullChar

    'Call the Shell_NotifyIcon function to add the icon to the taskbar
    'status area.
    Shell_NotifyIcon NIM_ADD, nid
    Me.Hide
in form_mousemove

Code:
    Dim msg As Long
    Dim sFilter As String
    msg = X / Screen.TwipsPerPixelX
    Select Case msg
        Case WM_LBUTTONDOWN
        Case WM_LBUTTONUP
        Case WM_LBUTTONDBLCLK
        Case WM_RBUTTONDOWN
            PopupMenu mnuSystray
        Case WM_RBUTTONUP
        Case WM_RBUTTONDBLCLK
    End Select
in form_unload / frm_terminate...

Code:
Shell_NotifyIcon NIM_DELETE, nid
This will create an icon (of form1) in the systray. When the user rightclicks on it, it will bring up the mnusystray menu created using the form menu editor.

Hope this helps