The GRAPES-3 (Gamma Ray Astronomy PeV EnergieS phase-3) is a globally recognized experiment that detects cosmic rays over 10$^{13}$ eV to 10$^{16}$ eV. It has an excellent core-resolution at PeV energies. We are planning for a radio-extension to the GRAPES-3 experiment and designing an array with 60-70 antennas. The array has been envisaged to work on the beam-forming approach to detect cosmic rays over the PeV energy range. We have used the beam-forming framework to optimize the design of our radio array. With the beam-forming technique, we are endeavoring to lower the radio-detection threshold down to few tens of PeV. Using CoREAS simulations, we have been able to demonstrate the detection of 10 PeV air-shower events, at the 4$\mathrm{\sigma}$ detection threshold. This may enhance the overall detection threshold of the GRAPES-3 experiment.