detecting specific "carrot on a stick" usage

I'm wanting to detect when a certain carrot on a stick is used, but first I want to detect when it is held. I'm not sure how to do this though, and help is greatly appreciated
these are manual commands right now, so that's why the / is there
command 1 : /give @p carrot_on_a_stick[custom_data={lifegiver:1b},custom_model_data=623001,custom_name='{"color":"black","italic":false,"text":"Lifegiver"}',enchantment_glint_override=true] 1
command 2 : /execute as @a[nbt={SelectedItem:{tag:{lifegiver:1b}}}] run say bah