I need to perform a sum of many (over 100) different cells and ranges that
are not in a continuous range. I could use the = function which would take
forever, and the sum function does not work when I try to add different
ranges that are not in a continuous order.

I know there is a simple way to do this...can anyone help - please?

Example: let's say I have these numbers in different cells
1,2,3,4,5,6,7,8,etc... and I want to add the cells that have the numbers
2,4,5 and 8. How can I add them without using the = or the sum function