Hey Manogr, other new divers, and even the ol' salts...
Dive tables support square dives ONLY! Don't try and make them do more by averaging. You are asking for trouble.
Computers and the Wheel (yikes) will support multi level diving. They are far more versatile and will accomplish the things you want to do. Get training in this and you will be well rewarded.
The Decoplanner and all of the other custom dive tables ARE ONLY FOR THOSE WHO ARE TRAINED TO USE THEM!!! Don't trade your life away for a few more minutes of dive time. Dive within... WELL within, your tables, wheels or computer. Don't feel that you have to push the envelope. We gots lots of people to do that for us. No matter if you are a Republican, Democrat, or Libertarian... BE CONSERVATIVE in your diving!!! As you can tell by the detailed nature of the discussion (and its not really detailed enough), there are more variables than you could possibly imagine at the moment. After you have gotten more than a hundred dives under your belt, seek out the tech programs and learn to dive to Titanic... just don't try it out tomorrow. It's OK to "just" be a recreational diver. Thats what I am!!!