I'm not sure exactly what a library is in this context but the program I'm using is very simple, basic maths and Boolean statements sort of thing, this is why I'm trying work out the raw maths behind the function...
there is no function in the program I'm using that i can find for norm cdf, I'm not sure what a library is in this context but i don't think the program would support it anyway, the program is limited to boolean logic, conditional statements, basic mathematics etc