有版友问能否如同Excel一样横向的求字段的平均值（其中如果字段值为空这不在平均值计算范围内），对于这个问题需要用自定义函数解决。在自定义函数中，要用到可变参数概念，也就是说需要适应带入的参数个数变化。这一方法是在事先无法确定参数数量情况下常用的一种方法。

Function DDMax(ParamArray A() As Variant) As Single
'示例:select *,DDmax(字段1,字段2,字段3,字段4) as 最大值 from 表1
Dim i As Long
Dim Mx As Single
Mx = -1 * 10 ^ 10
For i = 0 To UBound(A, 1)
        If IsNumeric(A(i)) = True Then
              If A(i) > Mx Then Mx = A(i)
        End If
Next
DDMax = Mx
End Function

Function DDMin(ParamArray A() As Variant) As Single
'示例:select *,DDmin(字段1,字段2,字段3,字段4) as 最小值 from 表1
Dim i As Long
Dim Mn As Single
Mn = 10 ^ 10
For i = 0 To UBound(A, 1)
        If IsNumeric(A(i)) = True Then
              If A(i) < Mx Then Mx = A(i)
        End If
Next
DDMin = Mn
End Function

Function DDAvg(ParamArray A() As Variant) As Single
'示例:select *,DDAvg(字段1,字段2,字段3,字段4) as 平均值 from 表1
Dim i As Long
Dim S As Single
Dim C As Long
S = 0: C = 0
For i = 0 To UBound(A, 1)
        If IsNumeric(A(i)) = True Then
              S = S + A(i)
              C = C + 1
        End If
Next
If C <> 0 Then
        DDAvg = S / C
Else
        DDAvg = 0
End If
End Function