子查询最多能返回一个记录

定义了如下函数：

Public Function NetWorkdays(dteStart As Date, dteEnd As Date) As Integer
Dim intGrossDays As Integer
Dim dteCurrDate As Date
Dim i As Integer
intGrossDays = DateDiff("d", dteStart, dteEnd)
NetWorkdays = 0
For i = 0 To intGrossDays
dteCurrDate = dteStart + i
If Weekday(dteCurrDate, vbMonday) < 6 Then
   If IsNull(DLookup("[HolDate]", "Holidays", "[HolDate] = #" & dteCurrDate & "#")) Then
       NetWorkdays = NetWorkdays + 1
   End If
End If
Next i
End Function

然后设置了查询：SELECT fromdddd.开始日期, fromdddd.结束日期, =(SELECT WorkingDays(开始日期,结束日期) from [fromdddd]) AS 工作日天數
FROM fromdddd;
但提示：子查询最多能返回一个记录

请高手指示如何解决，多谢！