Risk of ruin question

[uclaben]

I'm wondering if anyone here can answer this math question - I follow math well but I have no idea how to calculate this. Bonus points for anyone that can show me how to set it up in Excel, etc.

Given a standard limit hold-em buy-in (not bankroll), what is the risk of going broke in any given session?

Let's define the variables like this:

Buy-in: 20 BB
Win rate: 3 BB/100 (I mostly play live, so I think of it as 1 BB/hour at 33.3 hands/hour)
Variance/SD: You tell me, let's just assume a standard fill-in number

Time Period: 1 hour
2 hours
4 hours
8 hours
x hours

So the question is, at X hours, what is the likelihood that this player will have gone broke at some point leading up to that time demarcation? By the way, the practical application of this, as I imagine it, is "vacation" bankroll management: how much do I need to bring to be reasonably confident in playing a certain game in Vegas over an hour, day, weekend, etc.

Thanks in advance to anyone who puts in time on this. Appreciate it.