Private Declare Function WaitForSingleObject Lib "kernel32" (ByVal hHandle As Long, ByVal dwMilliseconds As Long) As Long
Private Const INFINITE = &HFFFF      '  Infinite timeout

Private Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)

Private Sub Command1_Click()
Dim cnr As SVAOuter.Host
Dim cn As ADODB.Connection
Dim hEvent As Long
    Set cnr = New SVAOuter.Host
    hEvent = cnr.Connect("provider=sqlncli;server=(local);database=qwe;trusted_connection=yes")
    If hEvent > 0 Then
        'Call WaitForSingleObject(hEvent, INFINITE) 
        'Одна проблема: оно будет ждать вечно.
        'При межпроцессном взаимодействии нужно при создании события изменять атрибуты безопасности, это мутная тема
        'Чтобы не морочить голову, возвращаемся к циклу со sleep
        While Not cnr.Connected
            Sleep 100
        Wend
        Set cn = cnr.Connection
    End If
End Sub

Option Explicit
Dim WithEvents cn As ADODB.Connection
Dim bConnected As Boolean

Public Function Connect(ByVal sConnString) As Long
    On Error GoTo errh
    Set cn = New ADODB.Connection
    cn.Open sConnString, , , adAsyncConnect
    Connect = 1
errh:
End Function

Public Property Get Connection() As ADODB.Connection
    Set Connection = cn
End Property

Public Property Get Connected() As Boolean
    Connected = bConnected
End Property

Private Sub Class_Terminate()
    Set cn = Nothing
End Sub

Private Sub cn_ConnectComplete(ByVal pError As ADODB.Error, adStatus As ADODB.EventStatusEnum, ByVal pConnection As ADODB.Connection)
    If adStatus = adStatusOK Then
        bConnected = True
    Else
        'следующая попытка
        cn.Open , , , adAsyncConnect
    End If
    'bConnected = True
End Sub