How to check if a item is in this exact slot in inventory

So am making a mod where if u right click a item it wont work unless it's in slot 4 but i cant figure out how to make the mod know it's in slot 4 it just doesnt know it am using mcreator 2022.2 for 1.16.5 

i have to be

if get item from slot 4 of the currently open GUI of event/target entity = item

do stuff that am too lazy to write since they arent being executed cuz of ^

else execute command /say Please put the item in slot 5

the code instantly goes to the else

it isnt detecting the fact that the item IS infact in slot 4