Changing image dynamically in crystal reports and vb .net 2008

What I am trying to achieve here is to change an image in a crystal reports .rpt file at runtime. Currently I am using code as shown below to pass custom test to parameters. How can I pass a bitmap to the report before exporting it as a PDF?

Public Sub DataPassOfficer()
        Dim Rep As New mg11a
        Dim passedvalue As String
        passedvalue = statementbody.TextBox1.Text
        Rep.ParameterFields(0).AllowCustomValues = True
        Rep.ParameterFields(0).CurrentValues.AddValue(passedvalue)
        Rep.ParameterFields(1).AllowCustomValues = True
        Rep.ParameterFields(1).CurrentValues.AddValue(Oforename + " " + Osurname)
        Rep.ParameterFields(2).AllowCustomValues = True
        Rep.ParameterFields(2).CurrentValues.AddValue("Over 18")
Rep.ExportToDisk(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat, "C:\temp\temp4.pdf")
   End Sub

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