请看看我的写的自定义函数，哪里出错了。

tongxue

自定义函数的功能是输入abcabk转成abck,即一串字符中重复的字符保留第一次出现的
Function 提取不重复字符(x As String)
Dim a As Integer
Dim b As Integer
Dim c As String
Dim d As String

For a = 1 To Len(x) - 1
c = Mid(x, a, 1)
For b = a + 1 To Len(x)
If c <> Mid(x, b, 1) Then
d = d & Mid(x, b, 1)
End If
Next b
Next a
提取不重复字符 = d
End Function

清风_ll

1. Function 提取不重复字符(x As String)
   
2. Dim a As Integer
   
3. 'Dim b As Integer
   
4. Dim c As String
   
5. Dim d As String
   
6. 
   
7. For a = 1 To Len(x)
   
8.     c = Mid(x, a, 1)
   
9.     If InStr(1, d, c) = 0 Then d = d & c
   
10. Next a
    
11. 
    
12. 提取不重复字符 = d
    
13. 
    
14. End Function
    

复制代码

tongxue

InStr(1, d, c)这是什么函数？一下子简化！