Please help me how to use the dataset accuratelty to perform the crystalreport.setdatasource

I have the following vb.net code

Protected Sub OfficeExecute_Click()

If page.isvalid=True then
    LoadReportData()
    Dim crystalReport as new reportDocument()
    crystalreport.load((Server.mappath("~/Reports/FollowUp.rpt"))'The Place where the crystalreport.setdatasource(...) statement should located
    CrystalReportViewer1.ReportSource=crystalreport
    Response.redirect(httpcontext.current.request.url.tostring(),True)
endif

End Sub

1. The underlying table which the crystal report use is "FollowUpReportSource"

2. I have a "~\App_Code\FollowUpDataSet.xsd" dataset which consists of only the table FollowUpReportSource.

3. The Fill query used to fill the FollowUpDataSet.xsd, is using parameter @UN (nvarchar(50) as following

SELECT        GNo, GRefNo, GSource, GSourceName, GSourceDesc, GTarget, GTargetName, GTargetDesc, GSubject, GPostDate, GPostType, GRequiredAnsPeriod, GProcessingStatus, GClosed, GImportance, GLate, No,
                         LetterID, Source, SourceName, SourceDesc, Target, TargetName, TargetDesc, PostDate, PostDateLong, PostType, ShownPostType, RequiredAnsPeriod, Importance, ActionAgainstLetter, LoggingUserName,
                         LoggingTime
FROM            FollowUpReportSource
WHERE        (LoggingUserName = @UN)

4. The value should passed to @UN = session("username")

5. my connection string already defined as myconnection.

According to the above, How to prepare the dataset and then use it in the CrystalReport.SetDataSource(...) ?