Multiple table calculations & referencing

Hi, please help.
I am not too handy with excel but have been building up a database for the last month and have been learning as I go. However, I am really stuck on two areas and cannot move past them. They are hard to explain so stay with me.
The first is that I have a value in a cell which is a long number. This number is the result of several calculations in another table. I need to enter this number in a separate row of data (probably more than once but this is variable) which then at the end of the row, is added up.

I need to enter the information quickly into this row and I don't want to copy and paste all the time. I also don’t want to have to set up a formula as this number won’t always be in the same cell in the row and may appear more than once. What I need is a one key shortcut so I can enter either a single number or letter (like '1' or 'A') into the row, the cell in the row will recognise what cell the number or letter relates too, pull the information and display it allowing the row to calculate it.

Is this possible and if so how do you do it?

My second problem is that I have three tables (just simple tables in the same sheets as the rest of my calcs) which I need to select data from based on variables.

At the moment I have been able to use an INDEX function to make the first table work, which has done so really well. What I want to be able to do now is link the remaining two tables to the same cell so that depending on various data the spreadsheet will look at the tables and selects the best one to provide the correct answer.

The best way to describe this is that the three tables represent the 2, 5, 10 times tables. My answer in one cell needs to direct the spreadsheet to look in the right table for the answer to a question.

I understand these things may not be possible but please let me know.

Many thanks in advance.

Welcome to the foruym, Miglia.

please take a few minutes to read the forum rules, and then amend your thread title accordingly.

Thanks.