Is Null in a Report

I'm using a list box to open a report for a specific record. I'm using a
report query for the report. The data in the list box updates the query. It
work fine except I would like to add some error handling before the report is
loaded. I would like to check to see if there is any data, if it is "null"
or no data provide a message box and exit before the report is loaded. I
cant seam to get pasted the if statement to check for the null. There must
be an easier way to get this accomplished. Any help would be appreciated.

Private Sub List14_AfterUpdate()
On Error GoTo Err_List14_Click

Dim stDocName As String
Dim stDocName2 As String
Dim stLinkCriteria As String
Dim stErrSiteNull As String

stDocName = "rptRebandingEquipFreq"
stDocName2 = "qryRebandingEquipFreq"
stErrSiteNull = "No Feeder System Set Yet, Try again Later!"
'open report Query and verify that there is data, if null close
query, message box and exit
DoCmd.OpenQuery stDocName2, acViewNormal
If IsNull(rs.Fields("SiteNum")) Then
DoCmd.Close
MsgBox stErrSiteNull, vbOKOnly, "Dude!"
GoTo Exit_List14_Click
Else
'If the query is not null close query and open report
DoCmd.Close
DoCmd.OpenReport stDocName, acViewPreview
End If

Exit_List14_Click:
Exit Sub

Err_List14_Click:
MsgBox Err.Description
Resume Exit_List14_Click

End Sub