VB+Access 数据库查询；总说参数不足这是怎么回事？？？

出错代码 Set rs = db.OpenRecordset(strSQL2)但类似的
Dim db As Database
  Dim rs As Recordset
  Dim num_fields As Integer
  Dim i As Integer
  Set db = OpenDatabase(App.Path + "\图书发行系统.mdb")
  Set rs = db.OpenRecordset("SELECT sum(数量*进价) as 进价总额,sum(数量*售价) as 售价总额 FROM SellBook WHERE 单据号 = '" + Data1.Recordset.Fields(0) + "' ")
  num_fields = rs.Fields.Count却执行的很好
这是怎么回事？？