you have to use some (global) variables to realize that idea.
for example you could create a table array with 32 entries (one for each player. have a look at the ut sounds sample). set the values to 0 at the beginning. you use this array for the timers/countdown!
when someone attacks you set the corresponding array field to 1. (which means: timer is active!)
the second hook checks all array fields. nothing happens if a field is 0 (inactive) but if it is >0 (=active) it will increase the field until it reaches the value 15. if it has reached 15 you set it to 0 again and equip the weapon.
OR you wait for the next release of CS2D which provides super useful timer functions. (no, I don't know when it will be released!)