List all sheets of opened workbook into ComboBox

[tmatematikas]

Hello everybody. I have such an isue: I'm tryin to list all sheets into ComboBox with VBA, here is the code:

Function ListSheets()
    Dim WS As Worksheet
    For Each WS In Worksheets
        ComboBox1.AddItem (WS.Name)
    Next WS
End Function
 
Function ClearSheets()
    Dim i As Integer
    Dim n As Integer
    n = ComboBox1.ListCount
    For i = n To 1 Step -1
        ComboBox1.RemoveItem (i)
    Next i
End Function
 
Private Sub ComboBox1_DropButtonClick()
    ClearSheets
    ListSheets
End Sub

Unfortunately, there comes out some kind of error (invalid argument) and I can not take ComboBox' text value to cell inside change() method.
If I change one method to as follows:

Private Sub ComboBox1_DropButtonClick()
    'ClearSheets
    ListSheets
End Sub

then the sheets are listed, but every time I click the ComboBox' button all sheets names just appends in the combo box. I've tried ComboBox1.Clear, but, situation is the same then: an error occurs. Any suggestion how to clear that ComboBox and fill again? Maybe that's something wrong with this code?