Javascript event to update checkbox on change of date/charge rate fields

I'm sure this is pretty simple

Could someone point me towards the best way to update a check box if a user opens updates a date field or a drop down field..

I'm thnking this will be some sort of javascript placed within the before update event

Air code
If storageexit date changes mark checkbox as 1
or
If empty bulk container date changes mark checkbox as 1
or
If storagerate changes mark checkbox as 1

Thanks in advance for any advice.