Option Explicit
 
 
 
Private Declare Function GetWindowLong _
    Lib "user32" Alias "GetWindowLongA" _
    (ByVal hWnd As Long, _
    ByVal nIndex As Long) As Long
Private Declare Function SetWindowLong _
    Lib "user32" Alias "SetWindowLongA" _
    (ByVal hWnd As Long, ByVal nIndex As Long, _
    ByVal dwNewLong As Long) As Long
Private Declare Function SetWindowPos Lib "user32" _
    (ByVal hWnd As Long, ByVal hWndInsertAfter As _
    Long, ByVal X As Long, ByVal Y As Long, _
    ByVal cx As Long, ByVal cy As Long, _
    ByVal wFlags As Long) As Long
 
Private Const GWL_EXSTYLE As Long = (-20)
Private Const WS_EX_TRANSPARENT As Long = &H20
 
Private Const SWP_FRAMECHANGED = &H20
Private Const SWP_NOMOVE = &H2
Private Const SWP_NOZORDER = &H4
Private Const SWP_NOSIZE = &H1
 
Public Function Transparent(ByVal hWnd As Long, _
    Optional ByVal Value As Boolean = True) As _
    Boolean
 
    Dim nStyle As Long
    Const swpFlags As Long = _
        SWP_FRAMECHANGED Or SWP_NOMOVE Or _
        SWP_NOZORDER Or SWP_NOSIZE
 
       nStyle = GetWindowLong(hWnd, GWL_EXSTYLE)
    ' Set new bits as desired.
    If Value Then
        nStyle = nStyle Or WS_EX_TRANSPARENT
    Else
        nStyle = nStyle And Not WS_EX_TRANSPARENT
    End If
    Call SetWindowLong(hWnd, GWL_EXSTYLE, nStyle)
        SetWindowPos hWnd, 0, 0, 0, 0, 0, swpFlags
       Transparent = _
        (GetWindowLong(hWnd, GWL_EXSTYLE) = nStyle)
End Function
 
 
Private Sub Check1_Click()
Call Transparent(RichTextBox1.hWnd, _
        (Check1.Value = vbChecked))
 
End Sub