Your Right Reyth... That is impossible.
I'm sorry Blue, but I've made a slight calculation error, which gave the wrong output :-(
Loosing with this system is actually more commen than previously expected and you would need somekind of progression.
I've attached the latest 100.0000 spins where my starting balance was 500... Not so uplifting I'm afraid.
You should know before even testing this system, that it can't be a winner.
Odds to win are 35/37 and odds to lose 2/37. No more no less. Just because 2 numbers didn't show up in a long series of spins, it doesn't mean that they have a contract that forbids them from showing up for one more spin.
Furthermore, one loss will have to be countered by 35 consecutive wins. And if another loss occurs during that period, you are looking for 70 wins before you start making any profit.
Who has the patience and the psychological strength to that?