Database Properties in GSA

First post here: I guess the best way to start off would be by explaining that what I'm trying to do for my workplace is probably a little bit over my head and above my paygrade but I'm determined to get this to work. Basically, what I'm trying to do is create a schema file that would allow me to pull multiple fields of data from an ODBC database by entering a value from a table and having the corresponding other fields load in response. 

What I'm working with is a BCPA_TAX_ROLL .mdb file that contains about 750k rows with information such as names, addresses, usage codes, etc. I also have a BCPA_GIS_POLYGON database that contains coordinates of each parcel, and a shape index database as well. How far I've gotten is this: I've been able to get the information I need to load in Bentley Map but the only way I can seem to do it is through running a VSQL query. Ideally, I'd like a ComboBox or something of the sort where I could enter an OBJECTID (the primary key that is linked throughout all databases) and have the fields I want pull up automatically - and then have the ability to append or attach that information to elements within Map. 

Really, it seems like everything I need to do has to be done within GSA but it's such a powerful program and I'm honestly just quite lost. I'm not sure whether I need to use a property watcher or multiple property watchers or really even how they work. I definitely understand some of the fundamentals of creating features and defining properties but I'm really just kind of running into a brick wall at this point.

I apologize if this is a really simple question or if I'm just doing something backwards. Any assistance at all would be greatly appreciated. I can take screenshots of the databases I'm working with if anyone needs them...but once again, I'm just losing myself in GSA. I've been looking at the online help and been through almost all of the training modules and I still can't seem to get this to work. Seriously, again - if this is just a dumb question or if I've confused anyone I'm really sorry. Thanks in advance for any assistance at all.