Solving Sum of Binomial Coefficients and Reducing to Exponential

Question

I want to solve the following equation:

$$\sum_{l=0}^{K-1} \binom{N-1}{l} {(1-\epsilon)}^l {(\epsilon)}^{N-1-l} \le \eta/\epsilon$$

and want to have expression of N as a function of $\epsilon, \eta$ and $K$.

Any hints/suggestions on how to solve/open the summation at the Left hand side of the equation ?

Thanks.