How do I base the value of one field, conditionally on another.

Hey guys, Access is not really my thing, and most of this project will be in Excel, but a particular series of entries could start becoming very large indeed, so its being suggested that Access might be a better solution for this particular data.

I'm using 2010 of all my office apps, and I guess my first questions is, how do I decide when to move over to Access from Excel? My Excel skills are coming along well, particularly my VBA, whereas I'm a total rookie with Access..

Well, coming back to my main question... and I did try google and such, but when you don't know the right terminology of a program that can be a little tough.

I've several fields where the value is based on another cell. For example if the field SIZE is 3 or less then the Class field will always be TINY,

4 or 5 SMALL,
5-7 MEDIUM,
8-11 LARGE
12-15 HUGE.

This is just an example, but there are several fields where the data will ALWAYS be the same as above, and no conditions will change this.

Can anyone suggest where I should be looking for the answer to this? Is it simpler to use excel (although then my point above applies), or better still some code examples that I can build on would be awesome.

Thanks guys in advance. If you need anymore data let me know.