Примерно так:
Dim vSQL As String
Dim vPass As String
Dim vLogin As String
Dim vConnection As ADODB.Connection
Dim vRecordset As ADODB.Recordset
vBase = LogForm.ComboBox1.Text ' если базу выбираем из combobox1
vLogin = "Login"
vPass = "password"
Set vConnection = New ADODB.Connection
vConnection.ConnectionString = "Provider=MSDAORA.1;Password=" + vPass + ";Persist Security Info=True;User ID=" + vLogin + ";Data Source =" + vBase
vConnection.Open
vSQL = "select distinct cl.name as n1, cl.clients_id as n2 " & _ ... и т.д.

Set vRecordset = New ADODB.Recordset
vRecordset.Source = vSQL
vRecordset.ActiveConnection = vConnection
vRecordset.Open
и выбираем записи
Do Until vRecordset.EOF
cl(i) = vRecordset.Fields("n2").Value