In UT '99?
There should be a class (I think it extends Object) in the OldSkool package, I believe it's called 'mappack', and has all the Default Properties for 'packing' your SP maps into a campaign playable through 'New Singleplayer game'. Like, you can change the splash logo, the title, all kinds o' stuff.
I haven't used the Ed in a while, I'm not sure all of what I'm saying is accurate. Just check it out for yourself, you'll see what I mean.