I am trying to automate my weekly travel itinerary, which is an excel sheet.

Ideally I would like to enter the destination into my itinerary, and then
automatically have the mileage displayed in another column in the same
sheet, and then have another sheet compiling my monthly mileage claim.

I sort of realise this will need a sheet to be matched to, i.e one sheet
showing the destination and mileage, my itinerary, and then the claim sheet.

Reason is that mileage is claimed quarterly, and its a nightmare going over
13 itinerary's and matching the mileage

Appreciate it anyone can point me in the direction where I can maybe work it
out.
Bob