Secondary item group - based on 3-digit item code

Hello,

How would one create a secondary item group section, next to the one that comes standard in the setup?

I would like to determine the item code on a set of parameters that need to be selected. I would need 3 types of item groups. I already have the code in place to determine the item code on the first item group, based on the example code in the help section on custom item coding.

example:

group 1 : beef > code 1
group 2 : salted, smoked > code 3
group 3: sliced > code 4

item code: 134xxx

or
group 1 : chicken > code 2
group 2: salted, smoked > code 3
group 3 : sliced > code 4

item code: 234xxx

where xxx is the running number in this particular section.

Thanks,

Thomas