How to Set Combobox selectedIndex property to -1?

Hello Guys,

I am creating 1 windows appl. and in that i had created onw function as follows

    Public Sub PopComboBox(ByVal objCombo As ComboBox, ByVal sTableName As String, ByVal sDisplayFieldName As String, ByVal sReferFieldName As String, Optional ByVal sAnyOtherField As String = "", Optional ByVal blnAddAll As Boolean = False)
        Try
            Dim SqlQuery As String = "Select " & Trim(sReferFieldName) & "," & Trim(sDisplayFieldName)
            If sAnyOtherField <> "" Then
                SqlQuery = SqlQuery & "," & Trim(sAnyOtherField)
            End If
            SqlQuery = SqlQuery & " FROM " & Trim(sTableName)
            Dim sSortOrder As String = sDisplayFieldName & " ASC"
            Dim SqlGenCmd As New SqlCommand(SqlQuery)
            Dim sqlDAGenCode As New SqlDataAdapter(SqlGenCmd)
            Dim dsForCombo As New DataSet()
            Dim dvForCombo As DataView
            If HasConnected = False Then
                OpenConnection(sDBName)
            End If
            SqlGenCmd.Connection = sqlConn
            sqlDAGenCode.Fill(dsForCombo, sTableName)

            dvForCombo = New DataView(dsForCombo.Tables(sTableName), "", sSortOrder, DataViewRowState.OriginalRows)
            objCombo.DataSource = dvForCombo
            objCombo.DisplayMember = sDisplayFieldName
            objCombo.ValueMember = sReferFieldName
            If blnAddAll = True Then
                Dim dRow As DataRow = dsForCombo.Tables(sTableName).NewRow
                dRow = dsForCombo.Tables(0).NewRow()
                dRow(sDisplayFieldName) = "-----ALL-----"
                dRow(sReferFieldName) = 0
                dsForCombo.Tables(0).Rows.InsertAt(dRow, 0)
            End If
            sqlDAGenCode.Dispose()
            dsForCombo.Dispose()
        Catch SqlEx As SqlException
            MsgBox(SqlEx.Message)
        Catch Proex As Exception
            MsgBox(Proex.Message)
        End Try
    End Sub

...... This function is called from the windows show events with the combobox and other parameters.

Now at the load event i written the code as
cmbMemberName.SelectedIndex=-1 .... but it is not working


please suggest me.

Thankx in advance.

Sanjeev