Here's the first attempt at creating the declining forward curve as shown in the screenshots from the book. At this time, I'm only focused on the non-stochastic part for now, the stochastic part to follow later.

Some things are not quite clear.....pls see the attached sheet and the comments below:

- Col S: F0 is the "original" fwd curve. I made this up using a simple decay. It's not a real forward curve of course, but it's the starting point.
- Col T: dF is the shock based on the equation I wrote out in my screenshot above. I used a fixed arbitrary one time shock of 20 (cell T7), enough to show a clear separation b/w the original and the new forward curve.
- Col U: F1 is the new shocked forward curve (F0 and F1 in the first cart at the top in COl V-AE)
- Col Q: "non_stoch", also represents F1, but as a direct solution (refer to hand written solution screenshot above). In this case, I don't need an explicit shock to create F1 (bottom chart in Col V-AE).
- Pls ignore all other charts and the columns I-N, greyed out font
- Things look fine so far...but one thing bothers me. As you can see, I'm using Col G (time) instead of H (ttm; T-t) to create F1. Clewlow's equation uses T-t, not just "t"......and if I switch to Col H, I get a weird chart....where the fwd curves separate "at the end". Pls do try it...just change the formula in Col Q and T to point to Col H instead of G.
- Using time to maturity in the calculation feels more natural....but I get the right results when I use the absolute time index "t"; not quite sure what to make of that right now - if you folks have a good explanation, pls do enlighten!

Anyways, this is what I have so far....more to come. Thanks!