如何让百分比总是出现在相应饼图扇区的中央位置？
如题，下面是我的代码，如何才能让百分比随着所在扇区角度的变化而变化，并且总是出现在该扇区的中央位置。

 Sub ShowPicture1(ByVal mBad As Integer, ByVal mVendor As String, ByVal Qty As Integer)
        Dim iFlags%
        Dim sql As String = ""
        Dim ds As DataSet
        Dim BMP1 As New Bitmap(Me.PictureBox1.Width, PictureBox1.Height)
        Dim BMP2 As New Bitmap(Me.P1.Width, P1.Height)
        Try

            sql = "select FIELD_DATA from udtKeyWord where KeyWord='Dining' and FIELD_TYPE='Title'"
            ds = SQLiteHelper.ExecuteDataset(connectstr, CommandType.Text, sql)
            If ds.Tables(0).Rows.Count > 0 Then
                Title_1.Text = ds.Tables(0).Rows(0).Item(0).ToString
            Else
                iFlags = vbInformation Or vbOKOnly
                MessageBoxTimeout(Me.Handle, "标题没有维护！", "Message", iFlags, 0, 3000)
                Exit Sub
            End If
            Name_1.Text = mVendor.ToString
            Dim i As Integer = 0
            Dim Sc As String = My.Computer.Screen.Bounds.Width.ToString & "*" & My.Computer.Screen.Bounds.Height.ToString
            'Dim MyGraphics As Graphics = Me.PictureBox1.CreateGraphics
            Dim MyGraphics As Graphics = Graphics.FromImage(BMP1)
            MyGraphics.Clear(Color.White)

            'Dim MyGraphicsP1 As Graphics = Me.P1.CreateGraphics
            Dim MyGraphicsP1 As Graphics = Graphics.FromImage(BMP2)
            Dim MyBrush As New SolidBrush(Color.Red)
            Dim MyProportion As Single
            Dim MyRect As New Rectangle
            Dim MyPoint As New PointF
            Dim R As Single
            Dim arrValues(1) As Integer 
 
            arrValues(0) = Qty
            arrValues(1) = mBad
            Dim arrValueNames(1) As String

            arrValueNames(0) = "总计：" + arrValues(0).ToString
            arrValueNames(1) = "不满意：" + arrValues(1).ToString
            'Const PI = 3.1415926
            MyGraphics.Clear(Me.PictureBox1.BackColor)
            MyGraphicsP1.Clear(Me.P1.BackColor)
            Dim MyStartAngel As Double
            Dim MySweepAngel As Double
            Dim MyM As Double
            Dim MyN As Double

            R = Math.Min(Me.PictureBox1.Width, Me.PictureBox1.Height) / 2 - 5
            MyPoint.X = Me.PictureBox1.Width / 2
            MyPoint.Y = Me.PictureBox1.Height / 2
            MyRect.X = MyPoint.X - R
            MyRect.Y = MyPoint.Y - R
            MyRect.Width = R * 2
            MyRect.Height = R * 2
            '画不满意扇区
            MyStartAngel = 0
            MyProportion = mBad / Qty
            MySweepAngel = 360 * MyProportion
            MyM = MySweepAngel
            MyBrush.Color = Color.Red
            MyGraphics.FillPie(MyBrush, MyRect, MyStartAngel, MySweepAngel)
            '画满意扇区
            MyStartAngel = MyStartAngel + MySweepAngel
            MyProportion = (Qty - mBad) / Qty
            MySweepAngel = 360 * MyProportion
            MyN = MySweepAngel
            MyBrush.Color = Color.Blue
            MyGraphics.FillPie(MyBrush, MyRect, MyStartAngel, MySweepAngel) 
 
            '画百分比
            If MyN = 360 Then
                MyGraphics.DrawString("满意 " + Math.Round(((Qty - mBad) * 100 / Qty), 2).ToString + "%", New Font("宋体", 12 * Me.Width / x, FontStyle.Bold), Brushes.Green, MyRect.X + R * 3 / 4, MyRect.Y + R)
            Else
                If MyN <> 0 Then
                    MyGraphics.DrawString("满意 " + Math.Round(((Qty - mBad) * 100 / Qty), 2).ToString + "%", New Font("宋体", 12 * Me.Width / x, FontStyle.Bold), Brushes.Green, MyRect.X + R, MyRect.Y + R * 3 / 4)
                End If
            End If

            If MyM <> 0 Then
                If MyM = 360 Then
                    MyGraphics.DrawString("不满意 " + Math.Round(((mBad) * 100 / Qty), 2).ToString + "%", New Font("宋体", 12 * Me.Width / x, FontStyle.Bold), Brushes.Green, MyRect.X + R * 3 / 4, MyRect.Y + R)
                Else
                    MyGraphics.DrawString("不满意 " + Math.Round(((mBad) * 100 / Qty), 2).ToString + "%", New Font("宋体", 12 * Me.Width / x, FontStyle.Bold), Brushes.Green, MyRect.X + R, MyRect.Y + R)
                End If

            End If
            Dim mW As Integer = Panel1.Width / 15
            Dim mH As Integer = Panel1.Height / 40
            Dim symbolLeg As PointF = New PointF(1, 10)
            Dim descLeg As PointF = New PointF(mW + 1, 10)
            '画杂项
            For i = 0 To arrValueNames.Length - 1


                MyGraphicsP1.FillRectangle(New SolidBrush(GetColor(i)), symbolLeg.X, symbolLeg.Y, mW, mH) 
 
                MyGraphicsP1.DrawRectangle(Pens.LightBlue, symbolLeg.X, symbolLeg.Y, mW, mH)

                MyGraphicsP1.DrawString(arrValueNames(i).ToString, New Font("宋体", 10 * Me.Width / x, FontStyle.Bold), Brushes.Navy, descLeg)

                symbolLeg.Y += 35
                descLeg.Y += 35
            Next
            PictureBox1.Image = BMP1
            P1.Image = BMP2
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub