Invoice field required check

Would it be possible to implement a feature where when you are creating say a sales invoice, the program will not let you save it until you have clicked ok - yes you have filled out your required fields.

I want to make two required fields (or rather check if I need to fill out the fields). I would like the program to ask me whether I want to put any serial numbers in the notes section on the sales invoice and whether I want to add delivery fees to the invoice! I will not need to add serial numbers or delivery fees for every invoice, so I think a customisable popup could be created (and activated for those who want the feature). We could fill out what we want the popup to say when we click on update for the sales invoice. The same principle could apply to purchase invoices.

I am always forgetting to add the delivery fee which I set as a sales invoice item! I realise not everyone will want this feature, so it could be a feature that is activated in settings for the forms you want. I want it for quotes, purchase invoices and sales invoices at this precise time, but I may want it for other forms in the future.

Can I bump this question up as well as I still keep forgetting to put serial numbers on the invoice which would be a good idea. I generally remember to add the delivery fee but would be useful to have that reminder.