Excuse me ! I made a mistake.

I supposed you use DAO objects since datPrimaryRS is the default name for the Data Control contained into VB generated code.

In fact I'm not an expert of RDO. But I guess there's a special syntax to set the ConnectString property. I know the correct manner with DAO (from VB books). Perhaps it's the same for RDO...
ConnectString is used by DAO to identify data sources provided by other engines (Paradox, dBase,ODBC). The syntax is "SOURCETYPE;SOURCENAME". For instance "ODBC;C:\Base\MyDB.sql".

I don't know if this can help you...