VBA Code to stop macro going any further if certain cells have data in them

Hi,
I am fairly new to Macro's and I have recently put together a Jobsheet spreadsheet for my client who is an Electrical Contractor.

So sheet 1 is the Job sheet form
Sheet 2 is the existing Customers database
Sheet 3 is the products list to be added to the form.

It is working fairly well except when it comes to preventing a double up by hitting the wrong macro button when selecting an existing customer from a drop-down list.

I have 2 Macro buttons side by side -
1 is to populate the rest of the customer's details into the top of the Job once you have selected the customer's name.
2nd one is to add a new customer by filling in the JobSheet fields and then clicking on the Save Macro button.

For the 2nd Macro button that saves a new customer to the list, I need VBA coding to produce a pop up asking say " Are you sure you want to Save this information as a new Customer " then supply a drop-down list with "yes/No" options
if "Yes" then a 2nd message pops up " Are all relevant customer details fields filled in " then supply a drop-down list with "yes/No" options
if "Yes" then the new customer is inserted into the Customers Table.
If No then the macro ends.

Any Help greatly appreciated

Use Exit Sub

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