Picturebox with Dartsboardimage - after clicked on, know what value?

If you want to define the darboard as multiple polygons then here is an approach that may work for you:

Imports System.Drawing.Drawing2D
Public Class Form1

    Private polygons As New ArrayList
    Private polygonNames As New Hashtable
    Private lastPolygon As GraphicsPath = Nothing

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim gp As New GraphicsPath


        Dim p(7) As System.Drawing.Point
        p(0).X = 365
        p(0).Y = 195
        p(1).X = 365
        p(1).Y = 195
        p(2).X = 393
        p(2).Y = 194
        p(3).X = 419
        p(3).Y = 195
        p(4).X = 416
        p(4).Y = 208
        p(5).X = 394
        p(5).Y = 207
        p(6).X = 368
        p(6).Y = 207
        p(7).X = 365
        p(7).Y = 195
        gp = New GraphicsPath
        gp.AddPolygon(p)
        polygons.Add(gp)
        polygonNames.Add(gp, "Triple 20 Area")

        ' create more polygons just like above...
        ' ...and add them to "polygons" and "polygonNames"
    End Sub

    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        Dim curPolygon As GraphicsPath = Nothing
        For Each polygon As GraphicsPath In polygons
            If polygon.IsVisible(e.X, e.Y) Then
                curPolygon = polygon
                Exit For
            End If
        Next
        If Not (curPolygon Is Nothing) Then
            If Not (lastpolygon Is curPolygon) Then
                lastPolygon = curPolygon
                PictureBox1.Refresh()
                Label1.Text = polygonNames.Item(curPolygon)
            End If
        ElseIf Not (lastPolygon Is Nothing) Then
            lastPolygon = Nothing
            Label1.Text = ""
            PictureBox1.Refresh()
        End If
    End Sub

    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        If Not (lastPolygon Is Nothing) Then
            Dim pen1 As New System.Drawing.Pen(Color.Blue, 3)
            e.Graphics.DrawPath(pen1, lastPolygon)
            pen1.Dispose()
        End If
    End Sub

    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        Dim curPolygon As GraphicsPath = Nothing
        For Each polygon As GraphicsPath In polygons
            If polygon.IsVisible(e.X, e.Y) Then
                curPolygon = polygon
                Exit For
            End If
        Next
        If Not (curPolygon Is Nothing) Then
            MessageBox.Show(polygonNames.Item(curPolygon))
        End If
    End Sub

End Class