关于用timer画动态图闪烁的问题

我用timer画一个动态图，但是每次都闪烁，而且程序有点卡，即使在timer里图形都不是一次性出来，都是一点点的显示，请教各位了，
我的源码:(mdata 是我从硬件得到的动态数据)
    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        Timer1.Enabled = False
        Dim pen As System.Drawing.Pen
        pen = System.Drawing.Pens.Red
        PictureBox1.Refresh()
        Dim xunit As Single
        Dim yunit As Single
        xunit = PictureBox1.ClientRectangle.Width / 3648
        yunit = PictureBox1.ClientRectangle.Height / 65535
        For i = 0 To 3647 Step 1
            PictureBox1.CreateGraphics.DrawLine(pen, xunit * i, 541 - yunit * Mdata(i), xunit * (i + 1), 541 - yunit * Mdata(i + 1))
        Next
        Timer1.Enabled = True
    End Sub