'определяет стиль окна 
Public Declare Function GetWindowLong Lib "user32" Alias "GetWindowLongA" (ByVal hWnd As Long, _ ByVal nIndex As Long) As Long
 'задаёт стиль окна 
Public Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, _ ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
 'устанавливает атрибуты(в том числе и прозрачность) 
Public Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hWnd As Long, _
ByVal crKey As Long, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
 'Константы 
Public Const LWA_COLORKEY = &H1
Public Const LWA_ALPHA = &H2
Public Const GWL_EXSTYLE = (- 20 )
Public Const WS_EX_LAYERED = &H80000


 'hWnd - манипулятор окна, Layered - степень прозрачности от 0 до 255 
Public Sub SetTransparent(hWnd As Long, Layered As Byte)
Dim Ret As Long
 'Определяем стиль нужного окна 
Ret = GetWindowLong(hWnd, GWL_EXSTYLE)
 'Задаём стиль окна как заслоённый 
Ret = Ret Or WS_EX_LAYERED
SetWindowLong hWnd, GWL_EXSTYLE, Ret
 'Задём степень прозрачности окна 
SetLayeredWindowAttributes hWnd,  0 , Layered, LWA_ALPHA
End Sub