If you can post a specific question I'm sure somebody here can help.
To get you started let's take the VAT problem. Let's say you have a price (ex VAT) in A1 then in B1 enter the formula
If you have a range of prices in Column A you can copy the formula in Column B down. To dio this hover the cursor over the bottom right corner of A1 and the cursor will turn into a +. Hold down the left mouse button and drag down as far as needed. This will copy the formula down; B2 will refer to A2, B3 to A3 and so on.