well, I've never done it before (been a while since I was really involved with windows), but I think you have set up an odbc data source using the access database and then compile an odbc module for tcl. Then you should be able to access the data. Good luck.
possibly an easier way would be to write a dde module and run the eggdrop on a windows box. it does have the downside of meaning that you'll have to have access running, but on the plus side it means that eggdrop would have direct access to most of access's features.
I used the DDE module to return information to mIRC, when processing complex scripts (that mIRC could not handle). I now use a DLL to call the script, and use the STDOUT + STDERR information to view returned data.
I found it would crash the oposite DDE party, rather than itself.
No, this was not a issue with mIRC, or any other DDE aware software. mIRC DDE interfaces with IE/netscape allmost all the time (to gain information on the currently viewed web-page).
I also have a few VB programs that interface with mIRC using DDE, without issue.
A ODBC module would do better.
Another option would be to create a exit macro in access (or module), that would export a CVS version of the table. This can be easily read by plain Tcl.
A import macro could do the same thing for startup.