vb组合框添加内容怎么防止重复

单击command1 添加text1的内容到combo1 代码如下
Private Sub Command1_Click()
For i = 0 To Combo1.ListCount - 1
Combo1.ListIndex = i
If Combo1.Text = Text1.Text Then
Exit Sub
End If
Next i
Combo1.AddItem Text1.Text
End Sub

Sub AddComItem(s As String)
Dim i As Integer
For i = 0 To ComboBox1.ListCount - 1
If s = ComboBox1.List(i) Then
MsgBox "已经添加", , "提示"
Exit Sub
End If
Next i
ComboBox1.AddItem s

End Sub

Sub Command1_Click()
AddComItem "1"
AddComItem "2"
AddComItem "3"
AddComItem "1"
AddComItem "2"
AddComItem "3"

End Sub