dreamweaver创建购物车的问题（asp）

我把购物车数据写在数据库里 每个用户有一个属于自己的购物车 现在想达到这样的效果：如果购物车中没有该BookId则插入购物车表中，如果已有该bookid则修改这本书的数量，目前的代码如下<%if (String(Request("MM_update")) == "form1") { if (!MM_abortEdit) { // execute the update var MM_editCmd = Server.CreateObject ("ADODB.Command"); MM_editCmd.ActiveConnection = MM_conBookshop_STRING; MM_editCmd.CommandText = "UPDATE dbo.Trolley SET [Number] = [Number]+?, Mail = ?, BookId = ? WHERE BookId = ?"; MM_editCmd.Prepared = true; MM_editCmd.Parameters.Append(MM_editCmd.CreateParameter("param1", 5, 1, -1, (String(Request.Form("numberset")) != "undefined" && String(Request.Form("numberset")) != "") ? Request.Form("numberset") : null)); // adDouble MM_editCmd.Parameters.Append(MM_editCmd.CreateParameter("param2", 201, 1, 30, Request.Form("mail"))); // adLongVarChar MM_editCmd.Parameters.Append(MM_editCmd.CreateParameter("param3", 5, 1, -1, (String(Request.Form("BookId")) != "undefined" && String(Request.Form("BookId")) != "") ? Request.Form("BookId") : null)); // adDouble MM_editCmd.Parameters.Append(MM_editCmd.CreateParameter("param4", 5, 1, -1, (String(Request.Form("MM_recordId")) != "undefined" && String(Request.Form("MM_recordId")) != "") ? Request.Form("MM_recordId") : null)); // adDouble MM_editCmd.Execute(); MM_editCmd.ActiveConnection.Close(); }}%><%if (String(Request("MM_insert")) == "form1") { if (!MM_abortEdit) { // execute the insert 略。。 }}%>前一段是修改 后一段是插入 求教该如何修改？