Expense database: newbie struggling with relationship / lookups
I'm really struggling to get this to work. I have an Expenses table to list individual business expense items, and in that table, I want also to select the VAT Rate description (Standard, Reduced, Zero or Exempt) which is applicable, from a drop down list. I also want to show the applicable % rate (15%, 5%, 0%, 0%) to then calculate the actual VAT for that item. I've tried a VAT table related to the Expense table, but whilst I can get the VAT Rate description to work in a drop down list, I don't know how to tackle the second bit, and to get this to calculate the actual VAT on that individual item.
What's the best way of doing this? Hope this makes sense!