In this paper we address a question of measuring a proton Structure Functions (SF) at Bjorken x\sim 1. A new method which allows for a measurement of SF at high x to be done with large data samples is proposed. Expected measurements after HERA luminosity upgrade are estimated using a Monte Carlo simulation. This shows that \sim 30 % precision can be achieved for the highest x-bins with 1{fb}^-1 of data in so far experimentally unconstrained region. Impact of this measurement on constraining the fundamental physics is discussed. A measurement with proton beam energy lowered to half (460 GeV) is discussed as well.

PACS numbers: 13.60.Hb, 14.20.Dh