He switched back to VBA and started typing. He didn’t copy-paste. He wanted to feel the logic. He declared his variables: x0 As Double , x1 As Double , tolerance As Double . He wrote a function called NewtonRaphson(FunctionName As String, guess As Double) .
Arjun’s eyes widened. He didn’t need calculus. He just needed two guesses.
At 7:55 AM, he emailed Helena the results. He attached a clean sheet with one button: “Calculate Vol.” He didn’t tell her about the PDF. He didn’t mention the cold coffee or the 11:47 PM panic.
Then he turned to Page 4.
He’d downloaded it six months ago and never read it. “Classic,” he sighed.
He ran it.
“You can’t solve for ‘x’ if it’s on both sides of the equation,” he muttered, sipping cold coffee. How To Code the Newton Raphson Method in Excel VBA.pdf
“If you cannot calculate the analytic derivative, use the Secant approximation: f’(x) ≈ (f(x + δ) − f(x)) / δ.”
Because next time the equation was impossible, he wouldn't be searching his downloads. He'd be ready.
He had spent two hours trying to use Excel’s Goal Seek. It was slow, clunky, and kept crashing when the volatility spiked above 200%. He needed speed. He needed precision. He needed the Newton Raphson method. He switched back to VBA and started typing
But he did rename the file.
Arjun leaned back. The PDF lay open on his second monitor. He realized the file wasn't just a tutorial. It was a key. For years, he had treated Excel like a glorified calculator. Now, he saw it as a numerical engine. The Newton Raphson method wasn't about roots—it was about control. It was about telling the computer, “Here is the rule. Now find the truth.”
The magic happened in the loop: