用vba写一个function，求两个数组的差集

可以使用 VBA 中的函数来求两个数组的差集，具体代码实现如下：

Function Difference(arr1() As Variant, arr2() As Variant) As Variant
    Dim diff() As Variant
    Dim i As Long, j As Long, k As Long
    Dim isFound As Boolean
    
    '初始化差集数组
    ReDim diff(0 To UBound(arr1))
    
    '求差集
    k = 0
    For i = 0 To UBound(arr1)
        isFound = False
        For j = 0 To UBound(arr2)
            If arr1(i) = arr2(j) Then
                isFound = True
                Exit For
            End If
        Next j
        If Not isFound Then
            diff(k) = arr1(i)
            k = k + 1
        End If
    Next i
    
    '输出差集
    ReDim Preserve diff(0 To k - 1)
    Difference = diff
End Function

在这个例子中，我们定义了一个名为 `Difference` 的函数，该函数接受两个数组 `arr1` 和 `arr2` 作为参数，并返回它们的差集。函数实现的过程与前面的例子类似，只是最后将差集数组作为函数的返回值输出。

可以在 VBA 编辑器中调用这个函数，并且将其返回的结果存储在一个变量中，例如：

Sub Test()
    Dim arr1() As Variant, arr2() As Variant
    Dim diff() As Variant
    
    '定义两个数组
    arr1 = Array(1, 2, 3, 4, 5)
    arr2 = Array(3, 4, 5, 6, 7)
    
    '求差集
    diff = Difference(arr1, arr2)
    
    '输出差集
    For i = 0 To UBound(diff)
        Debug.Print diff(i)
    Next i
End Sub