displaying next sequential number with the click of a button

[Grmcmrn]

We are getting rid of a piece of software that generates a sequential SKU for our stock parts and want to create a version in excel in the interim.

What I would like is to have a button to press that shows the next unused number from a list and will never show any of the previously used numbers to avoid duplication. There are also 3 letters before the sequential number that do not change.  

e.g press the button -> displays "ABC00000" ->press the button -> displays "ABC00001" etc. 

any suggestions would be appreciated 

[#2]

@Grmcmrn Mind if I ask how the list you're referencing is generated/updated?  e.g. are you pulling serial numbers from a database? 

I read this "e.g press the button -> displays "ABC00000" ->press the button -> displays "ABC00001" etc. " as implying the button will not only read from but also update the list.  

If that's not the case, can I ask why you want to press a button to return the next value when the formula can display it automatically whenever the list is updated?