Domain Mapping: A better way?

As previous discussions have noted (search: domain mapping multisite login), Domain Mapping causes problems with logins on Multi-site. So many of my site visitors have reported their frustration in getting logged in when I had Domain Mapping installed, I deactivated Domain Mapping from my sites. Now, users report they have no problem logging in to add their comments.

My question:

Given that I have several parked domains on my server that represent sub-sites of my primary domain, is there a script I can add somewhere on my server that will forward a request to a parked domain to my PrimaryDomain/ParkedDomain?

Thanks,

Ed