The Windows key is basically Ctrl+Escape.
And here's the code to call it.


Code:
Private Declare Sub keybd_event Lib "user32.dll" (ByVal bVk As _
Byte, ByVal bScan As Byte, ByVal dwFlags As Long, ByVal dwExtraInfo _
As Long)

Private Const KEYEVENTF_KEYUP = &H2

Private Sub Command1_Click()
    keybd_event vbKeyControl, 0, 0, 0
    keybd_event vbKeyEscape, 0, 0, 0
    keybd_event vbKeyEscape, 0, KEYEVENTF_KEYUP, 0
    keybd_event vbKeyControl, 0, KEYEVENTF_KEYUP, 0
End Sub