Pervasive error when Using date add function and using result in query

I have written a program that writes data to text files.  For one of the textfiles I need to check the date 30 days in the past and write the data results from that date forward.  The code I'm using is below and the error I receive is attached.  Any help is greatly appreciated!!  Thanks!!!

If System.IO.File.Exists(FILE_NAME) = True Then

            Dim LastMonth As Date = DateAdd(DateInterval.Day, -30, Date.Today)
            Convert.ToString(LastMonth)


            mySelectQuery6 = " "
            mySelectQuery6 = mySelectQuery6 & "SELECT DISTINCT APVendor.ID, CMCheck.CheckNo, CMCheck.CheckDate, CMCheck.Amount "
            mySelectQuery6 = mySelectQuery6 & "FROM APVendor INNER JOIN CMCheck ON APVendor.SKAPVendor = CMCheck.FKAPVendor "
            mySelectQuery6 = mySelectQuery6 & "WHERE(((CMCheck.Status) <> 2 And (CMCheck.Status) <> 34) AND (CMCheck.CheckDate > " & LastMonth & ")) "
            mySelectQuery6 = mySelectQuery6 & "ORDER BY CMCheck.CheckNo; "


        Else

            mySelectQuery6 = " "
            mySelectQuery6 = mySelectQuery6 & "SELECT DISTINCT APVendor.ID, CMCheck.CheckNo, CMCheck.CheckDate, CMCheck.Amount "
            mySelectQuery6 = mySelectQuery6 & "FROM APVendor INNER JOIN CMCheck ON APVendor.SKAPVendor = CMCheck.FKAPVendor "
            mySelectQuery6 = mySelectQuery6 & "WHERE(((CMCheck.Status) <> 2 And (CMCheck.Status) <> 34)) "
            mySelectQuery6 = mySelectQuery6 & "ORDER BY CMCheck.CheckNo; "

        End If
        'Pass the file path and the file name to the StreamWriter constructor.
        myCommand = New OdbcCommand(mySelectQuery6, myConnection)
        Dim objStreamWriter6 As StreamWriter
        objStreamWriter6 = New StreamWriter("C:\Rolligon\Data\POPayHist.txt")

        myConnection.Open()


        header(0) = "VendorID"
        header(1) = "ERP"
        header(2) = "CheckNo"
        header(3) = "CheckDate"
        header(4) = "CheckAmt"
        header(5) = " "
        header(6) = " "
        header(7) = " "
        header(8) = " "
        header(9) = " "
        header(10) = " "
        header(11) = " "
        header(12) = " "
        header(13) = " "
        header(14) = " "
        header(15) = " "
        header(16) = " "
        header(17) = " "
        header(18) = " "
        header(19) = " "
        header(20) = " "
        header(21) = " "
        header(22) = " "
        header(23) = " "
        header(24) = " "
        header(25) = " "
        header(26) = " "
        header(27) = " "
        header(28) = " "
        header(29) = " "
        header(30) = " "
        header(31) = " "
        header(32) = " "
        header(33) = " "
        header(34) = " "
        header(35) = " "
        header(36) = " "

        objStreamWriter6.WriteLine(String.Join(ControlChars.Tab, header))
        Try
            myReader = myCommand.ExecuteReader()
        Catch ex As OdbcException
            MsgBox(ex.Message)
        End Try
Pervasive-error.doc