clear a specific cookie from index.dat with ActiveX

I see tons of 3rd party tools for cookie management, but I'm trying to write an ActiveX command that will search for and delete a specific cookie. Actually, deleting the cookie is the easy part--deleting its reference from the index.dat is where I'm getting stuck.

It's not that I'm trying to block these cookies--just the opposite. The cookie is a visitor identifier that our hosted tracking system uses. When I delete the cookie through the browser, it deletes the cookie and wipes out the reference to it in index.dat, so that when I return to the site, it places a different visitor identifier tag on me. But when I try to write this into an ActiveX command, I can delete the cookie, but the ref in index.dat is still there, so when I return to the site, it remembers me and puts the same visitor identifier tag on me.

Any ideas how I can do this without purchasing a 3rd party solution?