Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" ( _
    ByVal hwnd As Integer, ByVal wMsg As Integer, _
    ByVal wParam As Integer, ByVal lParam As Integer) As Integer
 
    Private Const PBM_SETBARCOLOR As Integer = &H409
    Private Const PBM_SETBKCOLOR As Int32 = CCM_SETBKCOLOR
    Private Const CCM_FIRST As Int32 = &H2000
    Private Const CCM_SETBKCOLOR As Int32 = (CCM_FIRST + 1)
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Me.SendMessage(Me.ProgressBar1.Handle.ToInt32, PBM_SETBKCOLOR, 0, 354) _
        '// Der letzte Para. gibt die Farbe an
    End Sub