' Hier steht die Declare funktion von mciSendString, die kommplett funktioniert
Private Sub Cmd1Click(ByVal sender As System.Object,ByVal e As _
  System.EventArgs) Handles Cmd1.Click
mciSendString("open " & Microsoft.VisualBasic.Strings.Chr(34) & "C:\Video.avi" _
& Microsoft.VisualBasic.Strings.Chr(34) & " alias videostueck",0,0,0)
mciSendString("play videostueck",0,0,0)
End Sub

mciSendString("window videostueck handle " & pictureBox1.Handle.ToInt64( _
  ).ToString(),0,0,0)