I would like to know if its possible to create a sum total based
on categories selected in other cells.
For example, I have 3 categories: First, Additional & replacement. First
funnily enough is always the first number to be stated in the list, then
there can be any number of Additionals on top of that. Replacements however
override everything that has gone before it and effectively reset the sum to
what the Replacement is worth, Additionals can also be added on top of these
Replacements. Can I get a sum to intelligently see what categories are added
to a list as they are added and calculate the equivalent totals?

Eg

First 1
Add 1

Sum Shows 2

First 1
Add 1
Replacement 24

Sum shows 24


If anyone can understand what im trying to create and help me out that would
be fantastic.

Many thanks in advance,

Rikki

P.S. Is this in the correct section?