CALCULATE CORRECT VAT 10% ON A COMPLEX SPREADSHEET + BUTTON

I have a complex spreadsheet which calculates VAT at 10% for each expense. I need to update this to current 20% VAT. Also, I would like to have a button that will ask me which % VAT applicable ( 10 or 20%) and it will make the correct calculation . attached the spreadsheet. I need this by NO LATER than tomorrow the 25th at 9am AEST. Thanks