In Chaotic terms -- my opinion -- time is not linear. If you want to know "ahead" of time what the results of your sigil work will be, always do a divination. Even Master Therion (Crowley) divined before all works, and using his complex five stage readings (the ones where you ABANDON the read if your significator doesn't appear where it should) -- ultimately, the great mages throughout history considered magick more science than art. To progress in any order, from the Golden Dawn on, you had to "verify" results. I know this is what you're asking about, but if you do a divination, and your skills in that area are well-practiced -- and assuming you verify your divination as AC suggested in his five stage readings (recommended for any important works of magick) -- then you should achieve 100% success.
I do, but here's the thing. Many times I've created a sigil, complete with coding (time coding -- when it should happen; parameters coding; empowering coding), then when I've completed a thoughtful Tarot read, I've abandoned it. For example, your subconscious, connected to all of us through the Deep Mind (Dao, choose your language), is largely what makes sigils work. Your subconscious has awesome power, especially in the astral. The astral manifests in the physical. But asking for a million bucks by next Friday is bound to be a failure. Why, if it's supposed to work? Simply because there are other WILLS in the universe, there are other forces, there have to be conduits to manifestation. A divination will tell you all of this. It works this way in Servitor creation too. Or Ceremonial Magick. Or shamanism. Nothing replaces a good divination. Why go through all the effort only to have failure simply because you asked for too much, too soon. A divination will not tell you "yes/no" it will work. It will suggest why. Your subconscious mind will speak directly to you conscious mind, the mind creating the sigil. I use the three pillars (tree of life) spread with Thoth tarot for this, but choose your method. Celtic's fine. Particularly pay attention to any "outcome" cards. If you are indicating "failure" or "disappointment" there, look to the ADVICE cards (all spreads tend to have them, certainly Celtic, Tree of Life and AC's methods do). Then, based on that advice, try modifying your coding of your sigil. Do another divination. You'll find it's changed. Modify again if need be, until you discover the formula that will work.
Then, I assure you, if you KNOW you will succeed (the divination, via your subconscious (IMG:
style_emoticons/default/angel.gif) will tell you) and you CREATE your sigil (the power of creation... i.e. MAGUS) and you implant the sigil in your subconscious... you will achieve your result. Belief is important. What better way to achieve belief than to know in advance if you will succeed or fail. This way, in fact, you cannot fail, because you abandon what clearly won't work.