ComboBox event issue

[Scribe]

Hi guys,

I have a ComboBox which when entering focus I wish for it to populate itself with values from an SQL server.

At the moment I have:

        private void supplierNameBox_Enter(object sender, EventArgs e)
        {
            SupplierName.Clear(); //This is a table
            DbDataAdapter.SelectCommand = supplierNameSelectCommand;
            DbDataAdapter.Fill(DbMenuDataSet, "Supplier");
        }

However when my first click that brings the box into focus is the drop-down arrow, it somehow manages to duplicate the data entries, displaying them twice. Yet when i add a line such as:

MessageBox.Show("bla");

to the top of the function it works fine, except obviously I don't want a message box popping up!

Any help would be amazing guys.