It might be better to actually check for available SQL servers on
the network instead. Use the SQLDMO object model.
Once the user select the SQL server save it and upon the re-run
of the application load it into the cbo, but compare against active SQL servers.

Add the reference to "Microsoft SQLNamespace Object Library".
Code:
Public goSQLApp As SQLDMO.Application    
Public goNames As SQLDMO.NameList
    
'POPULATE CBO ONLY WITH SQL SERVERS
Set goSQLApp = New SQLDMO.Application
Set goNames = goSQLApp.ListAvailableSQLServers

cboServer.Clear
For i = 1 To goNames.Count
    cboServer.AddItem goNames.Item(i)
Next