Query code generating Invalid Use Of Null

Question

My code is generating an Invalid Use Of Null and I am not seeing the issue. When I compile the code, I do not get an error, but when I run and debug it, the error occurs at strRESMILE = rs("RESMILE").

Any thoughts? I can upload the database if need be.

    Sub COMPARE()
On Error GoTo err_COMPARE

 Dim db As DAO.Database
 Dim rs As DAO.Recordset
 Dim strSQL As String
 Dim strHold As String
 Dim strRESMILE As String
 Dim strRESMONTH As String
 Dim dblMILEAGEHold As Double
 Dim dblDATEHold As Double

 Set db = CurrentDb
 strSQL = "SELECT * FROM TABLE3"
 Set rs = db.OpenRecordset(strSQL)
 With rs
' If Not .BOF And Not .EOF Then
'        .MoveLast
'        .MoveFirst
    If Not .BOF Then
        strHold = rs("VIN")
        dblMILEAGEHold = rs("MILES")
        .Edit
        rs("RESMILE") = ""
        .Update
        .MoveNext
'While (Not .EOF)
        Do Until .EOF
            .Edit
            If rs("VIN") = strHold Then
                'do comparison
              If rs("MILEAGE") > rs("MILES") Then
                 rs("RESMILE") = "Y"
            Else
                rs("RESMILE") = "N"
              End If
            End If
            .Update
            strHold = rs("VIN")
            strRESMILE = rs("RESMILE")
            .MoveNext
'            Wend
        Loop
    End If
 End With

 Set db = CurrentDb
 strSQL = "SELECT * FROM TABLE3"
 Set rs = db.OpenRecordset(strSQL)
 With rs
    If Not .BOF Then
        strHold = rs("VIN")
        dblDATEHold = rs("MONTHS")
        .Edit
        rs("RESMONTH") = ""
        .Update
        .MoveNext
        Do Until .EOF
            .Edit
            If rs("VIN") = strHold Then
                'do comparison
              If rs("INSM") > rs("MONTHS") Then
                 rs("RESMONTH") = "Y"
            Else
                rs("RESMONTH") = "N"
               End If
            End If
            .Update
            strHold = rs("VIN")
            dblDATEHold = rs("RESMONTH")
            .MoveNext
        Loop
    End If
End With

rs.Close
db.Close
Set rs = Nothing
Set db = Nothing

MsgBox "Comparisons Completed!"

exit_COMPARE:
    Exit Sub

err_COMPARE:
    MsgBox Err.Description
    Resume exit_COMPARE

End Sub

Answer 1

Handle the evident NULL in your [RESMILE] field by using Nz().

So change strRESMILE = rs("RESMILE") to strRESMILE = Nz(rs("RESMILE"))