@Tisham-Dhar assuming you're using the hardware SPI and not bit-banging, I think it would be more straight-forward to use the designated SPI CS1 as the chip select, and then use a mux, with other GPIOs as control signals, to route the CS signal.

It's very likely possible to use the hardware controller with a GPIO CS signal, but it would likely involve quite a bit more work than the alternative.

Let me know how it goes!