Display “-” in place of an amount

Hello,

I recently purchased your Professional and Premium plugins.

Here is an example of a fictitious invoice I’ve generated.

I’d like to change the box on line 2, column 2. In the fictitious invoice, this is displayed with the amount €277.

I’d like a php code allowing me to :

For all items with the term “TVA sur marge” and the attribute “Régime de TVA”, to display the value “-” systematically.
This is the unit price excluding VAT, but these items are subject to a special system, so I need to display the price including VAT directly.

Thank you for your help,