I don't know of a formula but you can try this to see if it makes
calculating the VAT faster
type 17.5% in a blank, unused cell. click copy
highlight the area where you want to calculate the VAT (for instance
if you want to multiply all of column B by 17.5%, hightligth all of
column B)
Go to Edit->PAste Special -> select multiply and formulas (so you
don't change the formatting unintentionally) and hit ok
Everything that you highlighted will not by multiplied by 17.5%.
Alternatively.... you could use the product function.