first of all, use a boolean to check if event is on or not then hook player spawn into a function using hamsandwich library. from there you can use that function to show that menu.
here you have a little example:
PHP Code:
#include <amxmodx>
#include <amxmisc>
#include <hamsandiwch>
new bool:event
public plugin_init() {
RegisterHam(Ham_Spawn, "player", "menu_func", 1)
}
public menu_func(id)
{
if(is_user_alive(id) && event) // check if player is alive and event is on
{
// create menu and show it to player
}
}
public HappyHourCheck()
{
// code to check if happy hour is on or not
// if happy hour is on:
event = true
// else
event = false
}