ขอความช่วยเหลือค่ะ ต้องการ add ช่วงวันที่ของ start date กับ end date ใน sql

 Private Sub Btnabsent_Click(sender As Object, e As EventArgs) Handles Btnabsent.Click
        Dim iCheck As String
        Dim idate1 As String
        idate1 = CStr(Format(Dtpstrdate.Value, "yyyy-MM-dd"))
        Dim idate2 As String
        idate2 = CStr(Format(DtpEndDate.Value, "yyyy-MM-dd"))
        Dim datex As Date
        Dim iloop As Boolean = False
        datex = Dtpstrdate.Value



        If confirm("คุณต้องการเพิ่มข้อมูล หรือไม่?") = vbNo Then Return

        'For i As Integer = 0 To ts

        For i As Integer = 0 To DateDiff(DateInterval.Day, Dtpstrdate.Value, DtpEndDate.Value)

            sql = "select count(*) from tblLeave where [Job] = '" & txtjob2.Text & "'and StartDate = '" & datex.ToString("yyyy-MM-dd") & "'"

            iCheck = cx.ExecuteScalar(sql)
            ' Debug.Print(datex.ToString("yyyy-MM-dd") & " " & iCheck)
            If iCheck > 1 Then
                fail("ไม่สามารถ Plan ลาได้เนื่องจากฝั่ง'" & txtjob2.Text & "' มีคนลาครบแล้ว ในวันที่ " & datex.ToString("dd/MM/yyyy"))
                txtid2.Select()
                iloop = True
                Return
            Else
                sql = ""
                sql = "insert into tblLeave values('" & txtid2.Text & "','" & txtname2.Text & "','" & txtlastname2.Text & "','" & txtposition2.Text & "','" & txtA2.Text & "','" & txtBB2.Text & "','" & txtjob2.Text & "','" & txtzone2.Text & "','" & cboleave.Text & "','" & datex.ToString("yyyy-MM-dd") & "','" & idate2.ToString & "','" & txttotalleave.Text & "','" & txtcom.Text & "')"
                cx.Execute(sql)
                iloop = False
            End If
            datex = datex.AddDays(1)

        Next
        If iloop Then
            Return
        End If

        If cmd_excuteNonquery() = 0 Then
            fail("เพิ่มข้อมูลไม่สำเร็จ")
        Else
            ok("เพิ่มข้อมูลเรียบร้อยแล้ว")
            refresh_all_data_userid()
            txtid2.Text = ""
            txtname2.Text = ""
            txtlastname2.Text = ""
            txtposition2.Text = ""
            txtA2.Text = ""
            txtBB2.Text = ""
            txtjob2.Text = ""
            txtzone2.Text = ""
            txtphone.Text = ""
            cboleave.Text = ""
            Dtpstrdate.Value = Now
            DtpEndDate.Value = Now
            txttotalleave.Text = ""
            txtcom.Text = ""
            txtid2.Select()



        End If
    End Sub