pev_button (eq: EV_INT_button) = Buttons a client is pressing in the current frame.
pev_oldbuttons (eq: EV_INT_oldbuttons) = Buttons a client has pressed (released) in the last frame.
Generally both functionalities are hooked via
FM_CmdStart and
FM_CmdStop, afaik. Tho take in mind that both functions return a bitwise value, which means you can hook multiple buttons in this case.
https://www.amxmodx.org/api/hlsdk_co...buttons-values