Making an automatic numbered list in non-consecutive cells

[DeDe25]

Greetings to all.

We're a company that specializes in MEP installation, and we're currently making offers for the materials through excel lists, in which we detail the correspondent building story, the category (pipeline, electrical line, and such), the item itself (PVC pipeline sch 40 4"Ø), a description of the item, and all of the accesories or fittings that well need of this specific item. The issue is that when theres a new item that needs to be added, all of the code numbers need to be changed manually, which is extremely time consuming. We've searched for a way to make an automatic numbered list, but all of the methods we've tried so far only work if the cells are consecutive, hence they don't work on our list (due to the extra cells between each item's code number). We'd like to find a way to have all the code numbers change automatically when a new item is inserted, if possible. I've included an example of how our offer sheet looks. Thanks in advance!

[6StringJazzer]

There needs to be a way to identify which row needs a code number. Is LM always the line that gets a code?

Also, I did not follow what you meant saying the code numbers need to be changed. Once you add a new code number, why do other code numbers need to be changed? Do you add new items in the middle of the list and then renumber every item after that?

What is the next number after 10.09?

[6StringJazzer]

Have a look at this solution, formulas in column A.

[DeDe25]

Hello, and than you for your swift response. LM is always the line that gets a code, like the main item.

About the code numbers need changing, its because usually the added item is in the middle of the list, so all the codes need to be reaaranged in order.

And after 10.99 comes 10.100, 10.101 and so on.

[DeDe25]

Have a look at this solution, formulas in column A.

Amaizing, it works exactly as we needed it. So as long as the "LM" is preserved in every item that needs to be numbered, it will continue to number it. Also, after the number reaches 10.099 it resets back to 10.010, but it's still a great progress, compared to our current method.