为什么出现如下错误提示：aqReport:parameter strYear not found?

我有如下程序段：
begin
      if comboxMonth.Text=inttostr(2) then
      begin
          strsql := 'select * from tblHistoryRecords where date>=#39+strYear+#45+strMonth+#45+inttostr(01)+#39 and date<=#39+strYear+#45+strMonth+#45+inttostr(29)+#39';
      end
      else
        begin
          if ((comboxMonth.Text=inttostr(4))or(comboxMonth.Text=inttostr(6))or(comboxMonth.Text=inttostr(9))or(comboxMonth.Text=inttostr(11))) then
          begin
            strsql := 'select * from tblHistoryRecords where date>=#39+strYear+#45+strMonth+#45+inttostr(01)+#39 and date<=#39+strYear+#45+strMonth+#45+inttostr(30)+#39';
          end
          else
          begin
            strsql := 'select * from tblHistoryRecords where date>=#39+strYear+#45+strMonth+#45+inttostr(01)+#39 and date<=#39+strYear+#45+strMonth+#45+inttostr(31)+#39';
          end;
          with aqReport do
          begin
            close;
            sql.Clear;
            sql.Add(strsql);
            Parameters.ParamByName('strYear').Value:=trim(editYear.Text);
            Parameters.ParamByName('strMonth').Value:=trim(comboxMonth.Text);
            open;
          end;
        end;
运行之后。总是出现如下错误提示：aqReport :parameter  strYear  not found.
我在另一个程序段中曾经用过同样的程序段，运行挺好。这回不知怎么了？
请大家帮忙！