Can this be done? Question about Adding

I’ve been working on this app for several days. I have it fairly functional for my business, but now that it’s functional, I want it better! Here’s what I’m trying to do:

My business is similar to a magazine. We have main projects that we sell multiple advertisers into.

I have four main pieces of data:

Projects Tab - This is a list of all projects with unique numbers for those projects
Project Master Tab - this list holds clean data of all my unique project customers.
Advertisers Tab - Holds all information about each sale an advertisers has with us. It also includes the relations to the project tab and the advertiser master tab.
Advertisers Master Tab - this list holds clean data of all my unique advertiser customers. I’d like this list to be used simply to pull clean data for my sales.

So my question is this…each project is a combination of many new and current customers. I’m trying to find a way for my sales reps to add a new sales where they can either choose a current customer or add a new one.

Current customers are pulled from the Advertisers Master Tab. New customer’s need all information input by the sales rep. I would prefer that new customer information be required input. The hurdle is that I really need this to happen in the same space because sales reps get frustrated easily if they have to go different places to do different things.

I’ve done as much reading, testing and video watching as I can.

If the visibility option worked based on what was selected in the add form area, I could make it work, but that does not appear to be an option.

I’d simply like to ask the question, “Is this a new advertiser?”. If yes, then they must input all data, If no, they choose from list.

Ideas, thoughts, am I out of luck?

I should clarify that I would like the advertiser information input in the advertiser’s tab so that information related to the sale can be input at one time.

I don’t know if this fits your exact situation but I have a sheet with a list of competitions for students. In another sheet, I use the UNIQUE function to build a list of unique competition names. I then use that unique list to populate a choice component in a form. The form is used to add a new competition for a student. In my example, I allow the user to either type in a new competition name, or select from a list of existing competitions. This gives a warning in the builder because I’m using 2 components to fill the same column in the sheet, but it works great for me.