SQLFetch() on an unbound blob column is reading the entire blob into memory

Hello, I was wondering if there is anyway for SQLFetch() to avoid reading the entire blob into memory and chunk it one piece at a time via SQLGetData().    The product I work on is an isapi extention on IIS.  This products has a feature that allows users to store file attachments in the database as blob column types.  The problem we are seeing is when someone tries to access a very large file attachments.  The call to SQLFetch() reads the entire blob into IIS's memory prior to SQLGetData().   We'd like to store file attachments up to 500MB, but having to create