vba excel: do something every time a certain variable is changed

I'm doing a bunch of stuff to the variable St

For i = 1 To 30000

 Randomize
 e1 = Rnd
 e2 = Rnd
 z1 = Sqr(-2 * Log(e1)) * Cos(2 * 3.14 * e2)
 z2 = Sqr(-2 * Log(e1)) * Sin(2 * 3.14 * e2)

 St = So * Exp((r - (sigma ^ 2) / 2) * T + sigma * Sqr(T) * z1)
 C = C + Application.WorksheetFunction.Max(St - K, 0)
 St = So * Exp((r - (sigma ^ 2) / 2) * T - sigma * Sqr(T) * z1)
 C = C + Application.WorksheetFunction.Max(St - K, 0)
 St = So * Exp((r - (sigma ^ 2) / 2) * T + sigma * Sqr(T) * z2)
 C = C + Application.WorksheetFunction.Max(St - K, 0)
 St = So * Exp((r - (sigma ^ 2) / 2) * T - sigma * Sqr(T) * z2)
 C = C + Application.WorksheetFunction.Max(St - K, 0)


Next i

how do 开发者_开发知识库I get notified every time the variable changes?

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In the Excel VBE, you can add a "watch" to each variable. Select your variable, go to the Debug menu, click Add Watch... and then under Watch Type, click Break When Value Changes.

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maybe this a very naive answer but if you make a function that calls the sub then everytime a variable is changed then the function will be reevaluated.

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you can use breakpoints or dump St's value after every evaluation to a column on your excel file.

a very annoying solution would be to add message boxes all over the place

yet another clever solution would be to add logic to your code by declarin a variable that would store the previous value of St and then compare against it after the evaluation of the new St