probability of 3 in a row

Hi the probability of 1 occurance is about 1 in 10 what i would like to calculate is the probability of 3 of these happening in a row at any time across 500 trys .

If it happens twice but not 3 then we are reset to 0 so it has to be 3 in a row at any point in 500 trys

I tried to calculate as a binomial distribution but got a odd result

Thank you
I did do a quick simulation but I have just done it again more thoroughly, and this time got 35%+/- 1%. Sorry about that, chief. It may pay to do your own.
As a rough guide, there are about 500 chances, each of which is about 0.001 so the expected number is 0.05. If you approximate with the poisson distribution you get p(1 or more triple) = 1 - e^-0.05 which is about 39%