主题：检测一列的重复值，这些代码哪里有错？

以下内容为程序代码:

1 For i As Integer = 0 To Cot
2 Dim cfList As New List (of String)
3 Dim djID = CurrentTable.Rows(i)("物资信息_单据编号")
4 If cfList.Contains(djID) = False Then
5 cfList.Add(djID)
6 Else
7 Do
8 CurrentTable.Rows(i)("物资信息_单据编号") = Rand.Next(9999)
9 If cfList.Contains(djID) = False Then
10 cfList.Add(djID)
11 End If
12 Loop While cfList.Contains(djID) = True
13 End If
14 Next