Help with Loops

The comboboxes will rarely all be used but the option needs to be available. It's frmRecipes that I am referring to. When a product is purchased, it is added to the database in tblProducts, or a price change is made as required. The formulas in the green cells calculate the cost of each unit based on the total price paid.
When the user enters recipes, the information is stored in tblRecipes along with the food cost for that recipe. Therefore, I need to be able to calculate the cost of each ingredient in the recipe and then add them together for a recipe cost. Eventually this data will be used to cost out the menu plates as well but that step is down the road a bit.
Although I am quite familiar with entering formulas in spreadsheets, doing vba code in Excel is very new to me. This is quite an ambitious project for a newbie but if I get it accomplished - which I am determined to do with what will amount to a lot of help from this forum - then I will have a much better understanding of the whole thing.