Rather than worrying about ea sheet's name, maybe we can use the Workbook's SheetActivate event.

In ThisWorkbook module:
Private Sub Workbook_SheetActivate(ByVal Sh As Object)
    Dim wks As Worksheet
    Dim objMeComboBox As OLEObject
    If TypeName(Sh) = "Worksheet" Then
        Set wks = ActiveSheet
        On Error Resume Next
        Set objMeComboBox = wks.OLEObjects("ComboBox1")
        On Error GoTo 0
        If Not objMeComboBox Is Nothing Then
            With objMeComboBox.Object
                .Clear
                .AddItem "Item1"
            End With
        End If
    End If
End Sub
Does that help?

Mark