Urgent: Parameters of the Open-method

I work with Visual C++ 6.0 and an Oracle8 database. And want access to this database via ADO.
Now I have this code in C++:

_ConnectionPtr pConn;
pConn.CreateInstance(__uuidof(_Connection));

pConn->Open( ???)

But I don't know, how I must write the parameters of the Open-method.

Please help me.
Thanks Sascha

We are using something like this:

CString sCn;
sCn.Format("Provider=%s;Data Source=%s;User ID=%s;Password=%s",
"OraOLEDB.Oracle", "Oracle8ServiceName", "username", "password");

pConnect->Open((LPCTSTR)sCn, "", "", adOpenUnspecified /* -1 */);

That is.