I have this list of Products in my Product_Table.
In the top left corner you can see the Project that is selected - "27" in this case.
When I press the "+" button next to each item, I want it to add a new record to the Line_Item_Table related to the Project "27" and copy the fields: Cost_Price, Description & %_Markup from the selected record in Product_Table to the newly created record in Line_Item_Table and reference all the other related fields from Product_List and also make "Quantity" = 1. If the "+" button gets pressed again, then "1" is added to the quantity, but the record isn't added again. And of course if "-" is pressed then 1 is subtracted from the Quantity on that item from Line_Item_Table and if Quantity =1 then the record is deleted.
Does that make sense?