Zitat:

Ich programmiere einen Internetbrowser ...

Private Sub WebBrowser1_Navigating(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.WebBrowserNavigatingEventArgs) Handles _
  WebBrowser1.Navigating
        Dim DownloadableFile As Boolean = False
        Dim DownloadableExtensions$() = {"exe", "mp3", "zip", "rar"}
 
        For Each Extension As String In DownloadableExtensions
            If e.Url.ToString.EndsWith("." & Extension) Then
                DownloadableFile = True
                Exit For
            End If
        Next
 
        If DownloadableFile Then
            ' Navigation abbrechen
            e.Cancel = True
            ' Hier URL an den Download-Manager übergeben
            ' ...
        End If
End Sub