[vb6] Set the margins of a Textbox control

The VB Textbox control superclasses the Windows Edit window class, but doesn't implement its margin property. This procedure sets the left and right margins of a textbox control at run-time, with the margins measured in pixels.

    Private Declare Function SendMessageBynum& Lib "user32" Alias "SendMessageA" _
        (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, _
         ByVal lparam As Long)
    Private Const EC_LEFTMARGIN& = &H1&
    Private Const EC_RIGHTMARGIN& = &H2&
    Private Const EM_SETMARGINS = &HD3&
    
    Private Sub SetTextMargin(T As TextBox, ByVal mLeft As Integer, ByVal mRight As Integer)
      Dim lparam As Long
      lparam = mLeft + mRight * &H10000
      SendMessageBynum T.hwnd, EM_SETMARGINS, EC_LEFTMARGIN Or EC_RIGHTMARGIN, lparam
    End Sub