I think you have correctly seen the complexity of the problem. Cheers. The original question do not have a fix no. value. 30 trials is only a possible scenarios.
DislikedI think he meant what is the chance of the drawdown to be at least 10 units after 30 trades.
The excel formula doesn't work because you consider 10 winning to be enough but you forgot to consider 10 losses at the beginning of the trial.
There's no magic formula. You must calculate every possible permutation of winning and losses which is some N. For every permutation you must calculate if it goes to 10 DD, the sum of them being some M. The exact result is of course M / N.
As it is very hard your only chance is to generate a few million permutations...Ignored