The following macro will try to use the upper trinket (in slot 13). If successful, if starts a timer which plays a sound and prints a message in your chat window when the cooldown is over. If the trinket use was unsuccessful because it is on cooldown, it plays a different sound and prints a fail message to the chat window.
If you want it to work for the other trinket slow, change /use 13 to /use 14
It currently works for the Vengeance of the Illidari trinket, which in the wowhead TBC database is item 28040. You'll have to update that number for different trinkets. Also, the timer is set to 90, which is the 1 minute 30 seconds cooldown of the Illidari trinket. That might also need to be changed depending on the cooldown of the different trinket.
/use 13
/run local _,x = GetItemCooldown(28040)if x == 0 then C_Timer.After(90, function() print("Trinket ready!")PlaySound(11147) end)else print("Trinket not ready yet")PlaySound(10679)end