Correlation and Regression with variables Index

Hello, I need to create an index for the Likert items within the scale I am using in order to run a Correlation and regression test in SPSS. How do I create the Index?
Thank you in advance!
If you have 4 Likert items, for example y1, y2, y3 and y4. Then a usual way it to just sum them, like:

Index1 = y1 +y2+ y3 + y4.

Or you can,if you prefer that, you can give different weights to different items (like giving higher weight w1 to y1 if you think that y1 is more important than the rest).

Index2 = w1*y1 +w2*y2+ w3*y3 + w4*y4,

where w1+w2+w3+w4 = 1 (so that the weights sum to 1, just like the weighted mean.)

Now you can use Index1 or Index2 to calculate a correlation coefficient towards an other variable.
Is it a new column with the total of the scores by each participant?
There will be a new column (that is a new variable) for the new variable index. It will have one value for each participant ( =for each row).

In spss you create that by clicking on "compute a new variable" (or something like that. I don't remember exactly).
Interesting, then, there is a way in SPSS... I was thinking in that option in the excel table, and after to import the data from SPSS. Thanks a lot. I will explore SPSS options.
... I was thinking in that option in the excel table,
Excel?!! Oh, horror! Please, don't do it in excel!!

You point and click and after three months you don't remember anything of what you did. Your work should be reproducible.

Maybe you can use excel to enter the data (and control read it with a friend. (All of us makes mistakes. You too!))

Then read in the data to spss. Don't click on the "OK" button, click on the "Paste" button. That will give you a syntax file ( an *.sps file). There all your commands will be added. You save that file and re-use it next time you want to change or add something. Now, your work will be "reproducible", which is a good thing. And you will also have documentation of what you did. Write many comments, like:

* this is my index formula blah blah.

(A comment starts with a "*" and ends with a period ".".)