Open the crystal report in PDF on button click

Hello,
Generating report through passing parameter to Crystal Report,i need to open the report in PDF in new window on button click, i tried the following code
getting "Missing Parameter" Error
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
sysMonthRpt = New ReportDocument
sysMonthRpt.Load(Server.MapPath("SystemStatus.rpt"))
sysMonthRpt.SetDatabaseLogon("sa", "", "myServer", "myDB")
CrystalReportViewer1.ReportSource = sysMonthRpt
Dim myParams As New ParameterFields
Dim myparam As New ParameterField
Dim myDiscretevalue As New ParameterDiscreteValue
myparam.ParameterFieldName = "@tkMonth"
myDiscretevalue.Value = "12"
myparam.CurrentValues.Add(myDiscretevalue)
myParams.Add(myparam)
CrystalReportViewer1.ParameterFieldInfo = myParams
Dim oStream As MemoryStream
' using System.IO
oStream = DirectCast(sysMonthRpt.ExportToStream(CrystalDecisions.[Shared].ExportFormatType.PortableDocFormat), MemoryStream)
Response.Clear()
Response.Buffer = True
Response.ContentType = "application/pdf"
Response.BinaryWrite(oStream.ToArray())
Response.[End]()
End Sub
Any solution plz..
Thanks