The BitCoin bubble makes me want to re-implement a model I had in MathCad back in 2000 for the NASDAQ. I use Linux now, so no MathCad... But I do have Mathematica, but my skills are rusty.
Can you write something that:
(1) imports a date, price file from excel
(2) plots the data with a supplied formula
(3) Use sliders so the user can "eyeball" a fit
(4) take the slider values as seeds for an optimization (is this even possible?)
(5) implement a built-in optimization to get the best fit. (I worry that this last step might be time consuming, so I would want to limit your work here if it proves difficult).