DVD Writing Question - Decrypter

I'm just learning to use my DVD writer, using DVD Decryter.  I've studied
the instructions on doom9 as best I can, but here's my problem:

I want to make a compilation disc taking several chapters from each of 2
DVDs.  In simple terms, how can I do this using Decrypter, or is there a
better ripping program for this?  In IFO mode I can rip the chapters I want,
but how can I then re-number them, combine and write to DVD?

TIA.